Picking the Right Aquarium Filter

What things do you need to take into consideration when picking out a filter for your aquatic turtle? Which type of filter is best? Found out here.

A good filter is a big investment in your turtle's well-being. Not only that, a filter is by far the most important factor determining how much cleaning you'll have to do. A good filter will save you a lot of aquarium cleaning and general headaches associated with constant water changes.

Types of Filters

There are four common types of filters that you might consider for your turtle's aquarium:

In-tank Filter

These are small plastic tubes with a pump at the bottom. The pump sucks in water and fills the container above it. The water is forced through filter media to a recessed lip, where it falls back into the aquarium like a waterfall. These are not terribly efficient, and prone to jamming if not cleaned consistently. If the bottom side with the pump ever does clog, don't take it apart to clean. I broke two filters this way. Despite putting everything back together the same way, the pump would never work again. I've seen some rated to up to 20 gallons, but I just can't see one efficiently circulating enough water to keep that volume reasonably clean. Recommended only for small turtles in a small aquarium.

Decorative Filters

These are filters similar in design to the in-tank filters above, but have a sculpted rock face attached to make it look more natural. As with the in-tank variety, I don't see much use for these if you have older turtles or a larger habitat. Should be fine though if you have small turtles in a small aquarium.

Undergravel Filters

These are a little confusing because they work in a very unusual way. Instead of having separate filter media this type of filter uses the gravel or sand at the bottom of the habitat as the filter media. It works by having a pump pull the waste downwards through the gravel. Larger pieces of waste get stuck on top of the gravel while small debris is pulled down deeper and trapped below. The pump then cycles the water back upwards where it pours back down clean. We don't recommend these filters for many reasons. If you want to know why go to don't buy undergravel filters.

Canister Filters

Canister filters are the best type of aquarium filter currently on the market for aquatic turtles. They work by having a powerful water pump pull water out of the tank and force it through different types of filter media, then pumping it back into the tank. The best quality filters (like a Fluval or Eheim) have at least four types of filter media inside the canister. The first stage is a normal mechanical filter screen to remove large particles. Second is a finer screen to get small particles. Third is an activated charcoal pad which absorbs chemicals. Finally, water flows over a type of substrate created to house beneficial bacteria. A good canister filter will do all of this.

Our Recommendations

The type you should get depends mainly on the size of your tank and the number of turtles. If you have a small tank (10 gallons or less) and 2 or fewer turtles an in-tank filter ought to be fine. Just keep in mind that you ought to watch for algae growth and make sure that you keep the pump intake free of debris.

You need a canister filter if you have a larger aquarium. They have much larger capacities than the other types, and canister filters actually work well for turtles (unlike the undergravel filters as you can see below). Here are some guidelines you should keep in mind when purchasing an undergravel filter for your aquatic turtle:

  • Get a filter rated for roughly 2 to 3 times the capacity of your tank (turtles produce a lot of waste!)
  • Keep some extra filter media on hand if you don't want to have to track it down

Read Our reviews

We've reviewed 5 of the top filters and compiled detailed reviews for you. You can read them at our filter reviews page.

Don't Buy an Undergravel Filter

An undergravel filter sounds good, but in practice they don't work for turtles. These filters are meant to filter both biologically (by fostering healthy bacterial growth in the substrate) and mechanically (by pulling water through the gravel). However, that isn't really enough to properly clean the water.

Gravel does work as a filter medium as long as it stays undistubed and is always covering the pump intake. However, try telling a turtle not to dig! Turtles love to dig, so at least part of the time you'll end up with an uncovered (and thus non-functioning) filter. Not only does digging disturb the mechanical filtration, it also stirs up the bacteria growing below. When the bacteria is stirred up, all the bacterial waste and unprocessed turtle waste is put right back into the system.

Secondly, a canister filter simply filters things better. As I said in the section about canister filters, a good canister filter has a 4 stage filtration process. Compare that with the 2 stages of an undergravel filter (when its not being stirred up). I think the decision is pretty easy. A canister filter pulls the water out and filters it in 4 stages and an undergravel filter sucks the waste downwards and lets it rot at the bottom when its not being messed up by your turtles.

So please don't get an undergravel filter. You'd just be wasting your money. If you are curious, apparently they are not recommended for fish either!