Since aquatic turtles spend most of their time in the water, providing a proper enclosure for Aquatic Turtles means providing a clean and safe water space for the turtles to swim, exercise, eat, and even breed. Really no rocket science here, it’s just basic biology.

But going beyond this point is a bit more involved, and the obvious question becomes “just how do I go about keeping this water space clean and healthy for my turtles?”  Clean and healthy is a good way to put it, as water sources can definitely be clean or polluted, with either a healthy biosystem or an unhealthy one. Without a doubt, good water quality is one of the top priorities in keeping our Aquatic Turtles happy and healthy, and for most, some form of a water filtration system is the answer.

But this is where many beginning hobbyist in Aquatic Turtles start to get into territory they’re not familiar with, and questions about different filters and filtration products come up.  Some hobbyists have their own favorite examples of what has worked for them and are quick to recommend what to buy, but since aquarium situations vary (sometimes tremendously) their advice, although well meant, can very well lead you in the wrong direction. That is why it is important for you to understand what a filtration system for aquatic turtles provides, and how it provides it. Once you understand the basic principles, you will be very able to choose the best system on your own, appropriate for your particular set of circumstances. So, stick with us as we take you through the process!

The first thing to understand is that the filter you will eventually pick out will not be a filter for turtles. Most all the filters available to you are systems developed for fish and aquarium keeping. You might think this an odd statement since your turtles live in an aquarium, in the same aquarium water that fish would live, but turtles effect the water (and so the filtration) in ways fish do not.  Performance standards for aquarium filters are evaluated on how much of a “biological load” they can effectively handle. The biological load refers to the amount of pollutants the living things in the aquarium expel into the water, and how effectively the filter can process these pollutants and keep the water clean and biologically safe. This is accomplished by the amount of filtration material present in the filter, the type of filtration materials used, and the flow rate of the filter (how many times the filter can process the aquariums water per hour). Simply put, aquatic turtles tend to be very messy, on average a turtle tank with 2-4 turtles can produce up to 4 times the biological load then the suggested amount of fish for the same size aquarium. What does this mean to someone like you, looking to purchase a filter for your turtle tank? It means that you must look for a larger filter, with a larger biological load capacity then you normally would for your sized aquarium. Because turtles can dirty up their water far greater and faster than most fish can.

So, what are the main features to look for when choosing a good filtration system for aquatic turtles? The first is understanding what a filter for your turtle aquarium actually does. It obviously “filters” the water, but how? The first lesson to learn is, how does a filter, well…filter?

To start off, there are three basic stages of filtration that you will generally use with aquatic turtles. There are others, but these are the big three:

• Physical Filtration (or particle separation): This process simply passes the aquarium water through some form of material that traps the “physical” pollutants that are suspended in the water. These pollutants can be sand, silt, plant material, uneaten food partials, and even large chunks of waste products. A coffee filter is a good common example of this type of filtration, holding back the coffee grounds and allowing the water to pass through. Aquarium filters generally use sponges and material pads to trap these types of suspended particles. 
• Chemical Filtration (reactants and absorbents): This step is added to the filtration process after the suspended particle waste has been removed. The water is now passed through filtration products that remove chemical pollutants that are in solution with the water. Chlorine and chloramines that come in our drinking water are common examples of these undesirable chemicals. This step is usually accomplished by these filter products absorbing the chemicals directly as the water passes by/through them, activated carbon is a classic example of this type of filtration product.
• Biological Filtration (or biological conversion): This is generally considered the final step in the three-part filtration process. Now that the water has been stripped of physical suspended mater in step one, and many chemical pollutants have been filtered out in step two, the water is now passed over filter media that is colonized with nitrifying bacteria. These very beneficial bacteria biologically convert the toxic ammonia from the turtle’s waste products into less toxic Nitrite, and then into Nitrate. This “bio-media” can be some form of sponges, ceramic pellets, or plastic items within the filter. This bacteria also lives within the aquarium in gravel beds and on surfaces within the aquarium.

Good Aquarium filters will employ all three of these basic filtering stages within their design. What varies is how these filter stages are preformed and how the actual filter works. You will have a few choices to consider, but don’t worry, now that you know what an aquarium filter does the rest isn’t hard at all.

Next, there are three primary filter designs that you will be looking at that work well enough on most turtle tanks. You will most likely pick one (although multiple types can be used in tandem). Each as its pros and cons. Most employ the three stages of filtration we discussed above, but this could vary by brand. Let’s take a look at your three basic choices:

• HOB’s: Standing for “hang on back” these filters usually rest on the back or side lip of the aquarium. They are unpressurized systems that simply pull the water from the tank, pass the water through various stages of filter media, then allow the water to cascade back into the aquarium. They generally require an aquarium at least half to two-thirds full of water to work correctly. HOB’s are surprisingly effective in low/med bio-load applications, depending on the brand and filter media used, but the usually lower flow rates limit their use for larger turtle tanks.
• Internal Filters: These are filter units that submerge directly into the aquarium. Many work very well with low water levels for baby turtle setups.  They are generally physical filters with either sponge media or fiber cartridges so for larger setups they are inferior to other choices. They do however make a great additional filter for larger aquariums to increase water flow and to create extra current.
• Canister Filters: Canister filters are pressurized systems that are normally designed to operate alongside the aquarium or below it. Flexible hosing connects the filter to inlet and exhaust tubes positioned within the tank. The aquarium water is drawn out through these tubes, passed through various filter materials within the canister, and then is returned under pressure back to the aquarium. These filters are available in a surprising number of sizes and flow rates. The process of filtration is usually excellent with this choice of filter, but some brands can clog quickly with the turtle waste, and most are still a challenge to clean. Cost varies from brand to brand, some very reasonable, some very expensive. Most canister filters on turtle tanks should be broken down and cleaned monthly, but that will depend on the bio-load your turtles produce and your feeding regiment.

So now you are up to speed on what a filter for you turtle tank does and how it does it.  You also now know what types of filter choices there are to choose from. The final step to properly choosing a filtration system for your turtle tank is to evaluate your particular situation and decide what your budget is. Take your time and research some of the brands of filters that are available to you within your price range and what type of filtration they offer. You should now be ready to make a good, educated choice.

Here are some example scenarios that may help you put everything in perspective:

A Beginners setup for baby turtles: with a smaller tank, lower water levels, and a moderate water flow for hatchling/baby turtles, an internal filter should fit the bill. Its easily cleaned, provides adequate filtration for low water volume applications, and is generally low-cost.

Multiple turtles in moderate sized aquariums: with a medium size aquarium and a few assorted turtles not fully grown, an HOB works well. If you’re ok having the unit in full view, they can be very effective in high water level – lower bio-load applications (and are very affordable). Smaller to medium sized canister filters are also a good choice if the bio-load is heavier, or you’d like the unit out of view (though usually a bit pricier). Combining either of these options with an internal filter can add additional water flow and filtering capacity.

Larger turtles and larger Aquariums: with larger aquariums housing larger or more quantity of turtles, canister filters are likely your best choice. The increased bio-load and sheer volume of water to be processed in these large tanks can be best handled by these type of filters. Remember, a larger then suggested canister filter will handle the filtering process easier.

That’s the basics of what you need to know, good luck with your filter shopping, we hope the above article helped in answering some important questions in regard to how to filter your turtle’s aquarium.  We at Turtle-Tech are always here to assist you with specific situations you may have, please feel free to reach out to us with any future questions. 

A filtration side note:  One of the major contributors to cloudy, smelly, bad water quality is poor quality turtle food products and/or overfeeding. Please check out the Turtle-Tech article on the…

                                    “The Proper Feeding of Aquatic Turtles” 

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