There are many types of filters out there but the concept is the same. Nonetheless, there are differences between different types, duh. I’ll go through the main ones and what I think of them with regards to turtle keeping, whether you take my advise or not is entirely up to you.
This infamous filter that everyone seems to have. I personally and genuinely feel this filter is rubbish. Rubbish for what most people are using it for. If you have a box turtle and have a small water body for drinking and soaking, then this is fine. But as a filter for an aquatic turtle? Really bad.
BUT, better than nothing.
Great for fish, not so much turtles. Turtles will bite the sponge off bit by bit and push it round so much that you’ll end up with more problems. I would not recommend.
Not a bad starter filter, definitely better than the turtle filter. Works well for hatchlings up to 3-4inches. Any larger, your filter could not keep up with the waste and your turtle will probably be strong enough to shove your filter aside and potentially creating a water fountain, flooding your room. Good thing is it does not take up additional space outside the tank.
Hang-On-Back (HOB) Filter
This is a slight upgrade from the internal filter. It does not take up much space in the water or even outside the tank. This filter will work well up to juvenile turtles but you can still use it as a secondary filter in a bigger tank. Works better with high water level. If you ask me, not optimised for turtles.
Overhead Filter (OHF)
OHF provides one of the best biological filtration with low flow and ample media. Very popular amongst fish keepers for obvious reasons. Water gets pumped up and it trickles down at low pressure through a series of small outlets in the manifold. This trickle-down gives the biological media a lot of time to work on the ammonia and nitrite, making OHF really effective biological filters. But how does it fair for turtles?
Frankly, not so great to me. First and foremost, the pump is in the tank. You have to barricade the pump to prevent the turtle from dislodging the piping and emptying your whole tank water into your living room (my turtle is 8inches/20cm). I flooded my balcony multiple times because of those buggers. Secondly, turtle waste is big, it will clog your manifold and sponges often. You need to do a bit of modification. Good news, maintenance is as easy as lifting a lid off the tray. Also, it takes up space above your tank which means you will have less space to do an over-the-tank basking area if you wish to.
Canister filters are personally my favorite filter for turtles, as much as I tried to steer from it. Canister filters are generally robust. It forces water through the canister(housing) and pressurized it through all the media before going out. Because of this, it’s a better mechanical filter than OHF, but worse biological filter. Because it forces water through, it doesn’t really get clogged as easily. The bad thing about canister filter is, because it’s an all in one, if anything gets broken, you have to get an entirely new set. Also, cleaning is a nightmare and can get messy. Although you probably only have to clean it once in 2 months or so.
Let’s face it, nobody gets a sump filter for their turtles. It is expensive, it’s Arowana money. A sump filter is like having 2 tanks, one for your livestock and the other for just media. It is efficient, easy to maintain and you can add other peripherals such as UV filter. Takes up a lot of space though, it can easily be 2 – 3ft long. It is also known as overflow sump because the pump pushes water from the sump(housing) to the tank, the tank is overfilled with water and overflows back into the sump, through all the media. Drawback, it IS expensive. And because it is an overflow, the gunk from your turtles at the bottom of the tank will not get cleared off. Good filter? Yes. Optimised for turtles? No. Should you get it? Depends if you have Arowana money.
Firstly, don’t get gravel. I’m not gonna be one of those, ‘Oh no gravel! your turtle will eat it and die!’ bla bla bla. SHUT UP. Geez, some people hella preachy and loves to overreact. Okay, I’m done ranting. I don’t recommend gravel because you trade your tank aesthetics for more maintenance work. Gravel traps all kinds of dirt that no filter can satisfactorily remove, not even this undergravel filter.
Take a look at the overhead filter, how much pressure it lost on the multiple outlets on the manifold. Now look at this undergravel filter, instead of outlet, they are inlets to supposedly suck the whole base of the tank, through gravel! The pressure is negligible. It’s definitely not going to clean your gravel, but it does turn your gravel into some kind of additional bio media, not the reason you want this I’m sure.