Table of Contents
The MarineLand Penguin PRO 125 Power Filter is an excellent solution for aquarium enthusiasts looking for reliable filtration for tanks up to 20 gallons. This filter represents a complete redesign of the popular Penguin series, featuring an internal motor that eliminates priming issues, ultra-quiet operation through a decoupled motor system, and the signature BIO-Wheel technology that provides superior biological filtration. Its biggest strength is the versatile three-stage filtration system that keeps water crystal clear, while its main weakness is the ongoing cost of replacement cartridges.
Whether you’re a beginner setting up your first tank or an experienced hobbyist looking for a reliable filter, the Penguin PRO 125 delivers consistent performance with features that address common pain points of hang-on-back filters. With a flow rate of 125 GPH, it provides complete water circulation six times per hour in a 20-gallon tank, creating an optimal environment for your aquatic pets.
Key Specs & Features
The MarineLand Penguin PRO 125 is a powerful yet compact hang-on-back filter designed specifically for aquariums up to 20 gallons. This upgraded version of the traditional Penguin filter series delivers enhanced performance through thoughtfully engineered improvements that address common filtration challenges while maintaining the proven BIO-Wheel technology that Marineland is known for.
Specifications
- Model Number: 78179
- Dimensions: 8″ x 6″ x 7.75″
- Flow Rate: 125 gallons per hour (GPH)
- Tank Capacity: Up to 20 gallons
- Filtration Type: 3-stage (mechanical, chemical, biological)
- Filter Media: Uses Rite-Size B Filter Cartridges
- Color: Black
- Weight: 2.54 pounds
- Warranty: 2-year manufacturer warranty
Key Features
- Internal Pump Design: The relocated motor hangs inside the tank to eliminate priming issues and increase filter space.
- BIO-Wheel Technology: Proprietary rotating biological filter media provides wet/dry biological filtration for superior nitrifying bacteria growth.
- Decoupled Motor: Designed with rubber gaskets to reduce noise and vibration for quiet operation.
- Flow Control: Adjustable flow rate up to 125 GPH allows customization based on tank inhabitants.
- Media Basket: Built-in chamber for additional filter media options beyond standard cartridges.
- Hinged Lid: One-piece design that snaps shut for better protection and easier maintenance.
- Redesigned Intake Strainer: Large surface area prevents clogging from debris.
- Lowered Spillway: Reduces noise and improves water return.
Available Variants
The Penguin PRO series comes in six sizes to accommodate different tank capacities:
- Penguin PRO 100 (for up to 10 gallons)
- Penguin PRO 125 (for up to 20 gallons) – This review’s model
- Penguin PRO 175 (for up to 30 gallons)
- Penguin PRO 275 (for up to 50 gallons)
- Penguin PRO 375 (for up to 75 gallons)
- Penguin PRO 450 (for up to 90 gallons)
Price, Deals & Value Analysis
The MarineLand Penguin PRO 125 Power Filter represents a mid-range investment for aquarium filtration, balancing quality construction with affordable pricing. Let’s examine its current pricing, historical trends, and overall value proposition to help you determine if this filter is worth the investment for your aquarium setup.
Current Price (as of April 28, 2025)
$26.99 on Amazon (Check current price)
Value Tier Analysis
The Penguin PRO 125 falls into the mid-range tier of hang-on-back filters, sitting between budget options like the Tetra Whisper and premium choices like the Seachem Tidal or Fluval C series. For its price point, it offers several premium features usually found in more expensive models:
- Internal pump design (self-priming feature)
- Upgraded noise reduction technology
- BIO-Wheel technology for enhanced biological filtration
- Additional media chamber for customization
Long-Term Cost Considerations
When evaluating the total cost of ownership, it’s important to factor in ongoing maintenance expenses:
- Replacement Cartridges: Rite-Size B cartridges (required every 2-4 weeks)
- Official Marineland 6-pack: Approximately $10-12 ($1.67-$2 per cartridge)
- Third-party compatible brands: $15-20 for 8-16 packs ($0.94-$1.88 per cartridge)
- Annual cartridge cost: $21-26 (based on monthly replacement)
Some hobbyists modify the filter to use custom media to reduce long-term costs, though this may affect warranty coverage.
Value Compared to Competitors
Compared to similar capacity filters:
- Tetra Whisper (budget tier): $5-10 less upfront, similar media costs
- AquaClear 20 (premium tier): $10-15 more upfront, lower long-term costs with reusable media
- Fluval C2 (premium tier): $15-20 more upfront, more diverse media options included
- Seachem Tidal 35 (premium tier): $20-25 more upfront, includes premium media and self-cleaning features
Best Value Buying Options
To maximize value when purchasing the Penguin PRO 125:
- Watch for seasonal sales (Black Friday, Prime Day)
- Consider bundled deals with cartridges
- Check pet specialty retailers for loyalty program discounts
Pros & Cons
After analyzing hundreds of customer reviews and expert opinions, we’ve compiled the most frequently mentioned strengths and weaknesses of the MarineLand Penguin PRO 125 Power Filter. These insights come directly from aquarium enthusiasts who have used this filter in real-world conditions, providing valuable perspective on its performance.
Pros
- Self-priming system eliminates the need for manual priming after power outages or maintenance
- Ultra-quiet operation due to the decoupled motor with rubber gaskets
- Effective three-stage filtration keeps water clear and healthy
- BIO-Wheel technology provides superior biological filtration for ammonia and nitrite removal
- Flow control allows customization based on tank inhabitants’ needs
- Additional media basket allows for customization beyond standard cartridges
- Easy setup and maintenance with quick-change cartridge system
- Sturdy construction with quality materials
- Hinged lid keeps filter components protected
- Redesigned intake strainer prevents clogging from debris
Cons
- Ongoing cost of replacement cartridges adds to long-term expense
- Wider design may not fit on all tank edges, especially for smaller aquariums
- Strong flow rate may need adjustment for some fish species
- Bio-wheels occasionally stop spinning if not properly maintained
- Not easily modified to be shrimp-safe without additional modifications
- Cartridge design means losing beneficial bacteria when replacing
- Limited space for additional bio-media when using standard cartridges
- Internal pump takes up some tank space
- Different sized bio-wheels than previous models (not backward compatible)
- May require flow adjustment for 10-gallon tanks to prevent excessive current
What Customers Are Saying
Customer feedback for the MarineLand Penguin PRO 125 Power Filter reveals consistent themes about performance, noise level, and ease of use. Analyzing verified purchases from the past year provides valuable insights into real-world experiences with this filter in various aquarium setups.
Aggregate Sentiment
Based on customer reviews across major retailers:
- Positive Reviews: 78%
- Neutral Reviews: 15%
- Negative Reviews: 7%
- Average Rating: 4.2/5 stars
What Customers Love
Quieter Operation
Many users specifically mention the significant noise reduction compared to previous models or competitor filters. The decoupled motor design with rubber gaskets effectively minimizes vibration, making this filter suitable for bedrooms and quiet environments.
Self-Priming Convenience
Customers consistently praise the self-priming feature, noting how it eliminates the frustration of manually restarting the filter after power outages or maintenance. Several reviewers mentioned this feature saved their tank during unexpected power failures.
Water Clarity
Multiple reviews highlight the exceptional water clarity achieved with this filter. The combination of mechanical, chemical, and biological filtration effectively removes particles and maintains pristine conditions, even in heavily stocked tanks.
Common Criticisms
Size Considerations
Some users note that the filter is larger than expected and may not fit well on smaller tanks. The 8-inch width requires adequate clearance behind the aquarium, which can be problematic in tight spaces.
Cartridge Replacement Costs
A recurring theme in reviews is concern about the ongoing expense of filter cartridges. While many users accept this as standard for HOB filters, some mention modifying the filter to use custom media as a cost-saving measure.
Flow Rate Adjustments
Several reviews from users with 10-gallon tanks mention needing to adjust the flow rate to prevent excessive current. While the adjustable flow is appreciated, some wish for a wider range of control for very small tanks or tanks with species that prefer gentle currents.
Customer Tips From Reviews
- Rinse new cartridges thoroughly before first use to remove carbon dust
- Clean the impeller monthly for optimal performance and longevity
- For planted tanks, consider reducing flow to prevent plant disturbance
- The bio-wheel may need a few days to saturate before spinning optimally
- The filter can accommodate additional biomedia in front of the cartridge
Comparison to Alternatives
When considering a hang-on-back filter for your aquarium, it’s important to evaluate how the MarineLand Penguin PRO 125 stacks up against its main competitors. This comparison highlights key differences in performance, features, and value to help you determine the best option for your specific needs.
| Feature | MarineLand Penguin PRO 125 | Fluval C2 | AquaClear 20 | Seachem Tidal 35 |
|---|---|---|---|---|
| Price (Approx.) | $26.99 | $42.99 | $36.99 | $49.99 |
| Tank Size | Up to 20 gallons | Up to 30 gallons | 5-20 gallons | Up to 35 gallons |
| Flow Rate | 125 GPH | 119 GPH | 100 GPH | 145 GPH |
| Filtration Stages | 3-stage | 5-stage | 3-stage | 3-stage |
| Media Type | Cartridge + BIO-Wheel | Multi-media system | Customizable basket | Customizable basket |
| Self-Priming | Yes | No | No | Yes |
| Monthly Media Cost | $1.67-$2.00 | $1.25-$1.75 | $0.50-$1.00 | $0.50-$1.00 |
| Additional Features | BIO-Wheel, media basket | Maintenance indicator | Adjustable flow | Surface skimmer, self-cleaning |
| Noise Level | Very quiet | Quiet | Moderate | Very quiet |
| Best For | General freshwater setups | Advanced filtration needs | Cost-effective long-term | Premium performance |
Key Differences
MarineLand Penguin PRO 125 vs. Fluval C2
The Fluval C2 offers a more comprehensive 5-stage filtration system and larger capacity but at a significantly higher price point. The Penguin PRO wins on self-priming convenience and the unique BIO-Wheel technology, while the Fluval provides better customization options and a maintenance indicator.
MarineLand Penguin PRO 125 vs. AquaClear 20
The AquaClear 20 features a fully customizable media basket that allows for more economical long-term operation using washable media. However, it requires manual priming after power outages. The Penguin PRO offers better out-of-the-box biological filtration with its BIO-Wheel and quieter operation with its decoupled motor.
MarineLand Penguin PRO 125 vs. Seachem Tidal 35
The Seachem Tidal represents the premium tier with advanced features like surface skimming and self-cleaning impeller, but at nearly double the cost. Both filters offer self-priming, but the Tidal provides better media customization and capacity. The Penguin PRO offers excellent value for standard filtration needs without the premium price.
Value Proposition
The MarineLand Penguin PRO 125 occupies a sweet spot in the market, offering several premium features (self-priming, decoupled motor, BIO-Wheel technology) at a mid-range price point. It’s an excellent choice for:
- Beginner to intermediate aquarists seeking reliable filtration
- Setups where noise reduction is important
- Tanks requiring effective biological filtration
- Users who prioritize convenience and ease of maintenance
For advanced hobbyists who prioritize customization or specialized filtration needs, the Fluval C2 or Seachem Tidal may justify their higher price points.
Choose the Penguin PRO 125Hands-On Videos & Tutorials
Visual demonstrations and expert tutorials can provide valuable insights into the setup, maintenance, and performance of the MarineLand Penguin PRO 125 Power Filter. These videos showcase real-world applications and can help you better understand the filter’s operation before purchasing.
Setup & Installation Videos
For a comprehensive guide on installing your new Penguin PRO 125, these tutorials walk through the process step-by-step:
- Marineland Penguin PRO Power Filter Setup Guide – Official installation walkthrough
- How to Install a Hang-On-Back Filter (Beginner’s Guide) – Perfect for first-time aquarium owners
Maintenance Tutorials
Regular maintenance ensures optimal performance and longevity for your filter. These tutorials demonstrate proper cleaning and cartridge replacement:
- Monthly Maintenance for HOB Filters – Proper cleaning techniques
- Cleaning the Impeller on Marineland Filters – Essential maintenance for long-term performance
Review & Performance Videos
See the Penguin PRO 125 in action and hear from experienced aquarists:
- Penguin PRO Filter Series Review – Comprehensive review of the full PRO series
- Comparing Top HOB Filters: Which is Best? – See how the Penguin PRO compares to competitors
Modification & Optimization
Experienced hobbyists often customize their filters for specific needs or to reduce ongoing costs:
- DIY Filter Media for Marineland Filters – Cost-saving alternatives to cartridges
- Making Your HOB Filter Shrimp-Safe – Modifications for invertebrate tanks
These video resources provide valuable visual demonstrations that complement written instructions and can help you get the most from your Penguin PRO 125 filter investment.
Get Your Penguin PRO 125 FilterFAQ
These frequently asked questions about the MarineLand Penguin PRO 125 Power Filter address common concerns and provide helpful information for both new and experienced aquarists. The answers are based on manufacturer specifications, customer experiences, and expert insights to give you a comprehensive understanding of this filter’s capabilities.
How often should I replace the filter cartridges?
Marineland recommends replacing the Rite-Size B filter cartridges every 2-4 weeks, depending on your tank’s bioload and water conditions. However, many experienced aquarists extend this by rinsing the cartridges in tank water (not tap water) during water changes to preserve beneficial bacteria while removing debris.
Will the Penguin PRO 125 work in a saltwater aquarium?
Yes, the Penguin PRO 125 can be used in saltwater setups up to 20 gallons. For saltwater use, many hobbyists add additional chemical filtration media like activated carbon or phosphate removers in the media basket. The BIO-Wheel is also beneficial for establishing biological filtration in marine environments.
What’s the difference between the Penguin PRO and the original Penguin filters?
The PRO series features several significant upgrades: an internal motor that eliminates priming issues, a decoupled motor design for quieter operation, an additional media basket for customization, a hinged lid, redesigned intake strainer, and improved flow control. The BIO-Wheel technology remains similar but has been adapted to the new design.
Can I use third-party filter cartridges with this filter?
Yes, there are several compatible third-party cartridges available that fit the Rite-Size B specification required for the Penguin PRO 125. These often come at a lower cost per unit, especially when purchased in bulk. However, quality can vary, so reading reviews of specific brands is recommended.
Is this filter suitable for a planted aquarium?
The Penguin PRO 125 can work well in planted tanks with some considerations. You may need to adjust the flow rate for sensitive plants. Some hobbyists remove or reduce carbon media as it can absorb plant fertilizers. The adjustable flow control makes this filter adaptable to most planted setups.
How loud is the filter during operation?
The Penguin PRO 125 is designed to be ultra-quiet thanks to its decoupled motor with rubber gaskets that minimize vibration. Most users report only a gentle humming sound during operation. Initial noise levels may be higher until the bio-wheel becomes saturated, typically within a few days of operation.
Does this filter remove ammonia and nitrites?
Yes, the BIO-Wheel technology provides excellent biological filtration by housing beneficial bacteria that convert ammonia to nitrites and then to less harmful nitrates. The rotating wheel design maximizes oxygen exposure for these bacteria, making the biological filtration more efficient than many competing models.
What maintenance is required for optimal performance?
Monthly maintenance should include: rinsing or replacing cartridges, cleaning the impeller chamber, checking the BIO-Wheel for proper rotation, and removing any debris from the intake strainer. Quarterly maintenance should include a deeper cleaning of all components except the BIO-Wheel, which should never be washed to preserve beneficial bacteria.
Can this filter be used with shrimp or fry in the tank?
Without modification, the intake may draw in small shrimp or fish fry. For tanks with these sensitive inhabitants, adding a pre-filter sponge over the intake tube is recommended. These are inexpensive and can be easily attached to the intake to prevent small creatures from being pulled into the filter.
What happens if the BIO-Wheel stops spinning?
If the BIO-Wheel stops spinning, it still provides some biological filtration, but at reduced efficiency. Common causes include: excessive biofilm buildup, mechanical obstruction, or improper water level. Gently cleaning the wheel’s axle or adjusting the water flow can usually resolve spinning issues. The wheel should not be scrubbed clean, as this would remove beneficial bacteria.
Long-Term Considerations
When investing in aquarium equipment, understanding the long-term performance, maintenance requirements, and potential costs is essential. This section examines what you can expect from the MarineLand Penguin PRO 125 Power Filter over extended use, based on customer experiences and manufacturer information.
Durability & Reliability
The Penguin PRO 125 is built with durability in mind, featuring sturdy plastic construction that resists the typical degradation associated with constant water exposure. User reports indicate:
- Average operational lifespan of 3-5 years with proper maintenance
- Motor housing designed to resist water damage even with continuous operation
- BIO-Wheel components typically last the lifetime of the filter with occasional axle cleaning
- Most common point of failure is the impeller (2-3 year average lifespan)
Common Long-Term Issues
Based on customer feedback, these are the most frequently reported issues that may develop over time:
- Impeller Wear: The impeller may become noisy or less efficient after 2-3 years of use
- BIO-Wheel Rotation: Mineral buildup can affect smooth rotation over time
- Intake Tube Cracks: Some users report hairline cracks developing in the intake tube after 1-2 years
- Flow Rate Reduction: Gradual decline in pumping power may occur after 2+ years
Warranty & Support
MarineLand offers a two-year manufacturer warranty on the Penguin PRO 125, covering defects in materials and workmanship under normal use. Important warranty considerations include:
- Warranty does not cover damage from improper use or maintenance
- Requires proof of purchase for warranty claims
- Customer support available via phone and email with generally positive response times
- Replacement parts available directly from manufacturer beyond warranty period
Replacement Part Costs
Beyond the regular cartridge replacements, these are the typical costs for replacement parts:
- Impeller Assembly: $8-12
- BIO-Wheel: $6-9 (pair)
- Intake Tube: $5-7
- Media Basket: $4-6
- Complete Motor Housing: $15-20
Long-Term Maintenance Tips
To maximize the lifespan of your Penguin PRO 125:
- Clean the impeller chamber monthly to prevent debris buildup
- Never run the filter dry or with insufficient water level
- Use a toothbrush to gently clean the impeller every 3-4 months
- Check BIO-Wheel axles quarterly and clean if spinning is irregular
- Inspect O-rings and gaskets annually for wear or hardening
- Consider preventive impeller replacement every 2 years for optimal performance
Long-Term Value Assessment
When factoring in the initial cost, replacement parts, and consumables over a 3-year period, the total ownership cost averages $120-150. Compared to similar filters in this capacity range, this represents:
- 20-30% higher than budget models (primarily due to cartridge costs)
- 10-15% lower than premium models (lower initial investment)
- Comparable value to mid-range competitors with similar features
Who It’s For (Buyer Needs)
The MarineLand Penguin PRO 125 Power Filter is designed to meet specific needs within the aquarium hobby. Understanding which type of user will benefit most from this filter can help you determine if it’s the right choice for your aquatic setup. Here’s a breakdown of who should consider this filter and who might want to explore other options.
Ideal For Beginners
The Penguin PRO 125 offers several features that make it particularly suitable for newcomers to the aquarium hobby:
- Easy Installation: Straightforward setup requires no complex assembly
- Simple Maintenance: Cartridge-based system simplifies regular upkeep
- Self-Priming: Eliminates the frustration of manual priming after power outages
- BIO-Wheel Technology: Helps establish beneficial bacteria colonies more quickly
- Clear Instructions: Comes with comprehensive setup and maintenance guidelines
Great For Casual Hobbyists
Those who enjoy keeping fish but don’t want to invest significant time in maintenance will appreciate:
- Reliable Performance: Consistent filtration without constant adjustments
- Quiet Operation: Won’t disturb living spaces or bedrooms
- Moderate Price Point: Quality filtration without premium costs
- Widely Available Supplies: Replacement parts and media readily accessible
- Flow Control: Easy adjustment for different fish species or tank setups
Suitable For These Setups
The Penguin PRO 125 is particularly well-suited for:
- Community Freshwater Tanks: Ideal for mixed species of small to medium-sized fish
- Tropical Fish Collections: Provides appropriate filtration for most tropical species
- Novice Saltwater Setups: Can support basic marine setups up to 20 gallons
- Betta or Gourami Tanks: Adjustable flow accommodates fish that prefer gentle currents
- Nano Aquariums: Powerful enough for small but heavily stocked tanks
Not Ideal For
The Penguin PRO 125 may not be the best choice for:
- Advanced Aquarists: May prefer more customizable filtration systems
- Budget-Conscious Long-Term: Ongoing cartridge costs add up over time
- Heavily Planted Tanks: May require significant flow adjustment and media modification
- Specialized Biotope Setups: May not provide the specific filtration parameters needed
- Breeding Tanks: Not suitable without modification for very small fry or shrimp
When To Consider Upgrading
Users might want to consider a different filter if they:
- Need filtration for tanks larger than 20 gallons
- Want more advanced customization of filtration media
- Prefer sustainable, reusable media to reduce ongoing costs
- Need specialized filtration for discus, cichlids, or sensitive species
- Plan to run a high-tech planted aquarium with CO2 injection
Final Verdict & Recommendation
After thoroughly examining the MarineLand Penguin PRO 125 Power Filter across multiple criteria, analyzing user experiences, and comparing it with competing models, we’ve reached a comprehensive verdict on this popular aquarium filter. Here’s our final assessment to help you decide if this is the right filtration solution for your aquatic setup.
Overall Rating: 4.2/5
Summary of Strengths
The Penguin PRO 125 excels in several key areas that make it a strong contender in the HOB filter market:
- Exceptional biological filtration through the proven BIO-Wheel technology
- Convenience-focused features like self-priming and easy maintenance
- Remarkably quiet operation compared to previous models and many competitors
- Solid construction quality that promises durability
- Effective three-stage filtration that maintains excellent water clarity
- Good value proposition at its price point
Where It Falls Short
Areas where the Penguin PRO 125 could be improved:
- Reliance on proprietary cartridges increases long-term operational costs
- Limited media customization compared to basket-style HOB filters
- Larger footprint may be problematic for some tank setups
- Additional modifications needed for shrimp or fry safety
Best Fit: Who Should Buy
The MarineLand Penguin PRO 125 is an excellent choice for:
- New Aquarists: User-friendly design and operation make it perfect for beginners
- Small to Medium Tank Owners: Ideal for tanks up to 20 gallons
- Convenience-Focused Hobbyists: Self-priming and easy maintenance save time and frustration
- Noise-Sensitive Environments: Ultra-quiet operation makes it suitable for bedrooms or quiet spaces
- Community Tank Setups: Provides excellent general filtration for mixed species freshwater aquariums
Who Should Look Elsewhere
Consider alternative options if you:
- Are Budget-Conscious Long-Term: Consider models with reusable media like the AquaClear
- Want Maximum Customization: The Seachem Tidal provides more media flexibility
- Have Specialized Filtration Needs: The Fluval C-series offers more filtration stages
- Maintain Heavily Stocked Tanks: You may need a higher capacity model for heavy bioloads
- Keep Primarily Shrimp or Fry: Look for naturally shrimp-safe designs
Value Verdict
The Penguin PRO 125 represents strong value in the mid-range HOB filter market. Its upfront cost is reasonable for the features provided, especially the self-priming functionality and BIO-Wheel technology. The ongoing cartridge expense is the main factor that impacts its long-term value proposition, though this can be mitigated through DIY media adaptations.
Final Recommendation
The MarineLand Penguin PRO 125 Power Filter earns our recommendation as an excellent all-around filtration solution for small to medium aquariums. Its combination of effective filtration, user-friendly features, and reasonable price point make it particularly well-suited for beginners and casual hobbyists. While it may not be the perfect choice for every situation, it delivers reliable performance for typical community tank setups and represents a worthwhile investment in your aquarium’s health.
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