tiny-plastic-dead said:

I am a middle school teacher with a red-eared slider in my classroom. I am really struggling to keep the water clear - right now it's kind of yellowish. In the past, it has been clearer than it is now, and also bright green. Nothing I seem to try works, and I am concerned about the health of my animal. Right now my setup includes an enormous out-of-tank canister filter. What am I doing wrong?

Well, it could be a lot of things. The main causes are too much light (especially if it’s coming from a window) or high nitrates. For green water, at least.

How big is the tank? I’m willing to bet it’s a either too small or you’re not doing enough water changes- or both. The rule is 10 gallons of water per inch of shell length so if it’s a full grown male he needs a 75gal and a female needs a 100gal.

Canister filters are great, but all tanks need water changes. Turtles are high waste producers so water changes might need to be weekly. Do you have a test kit? If you can, buy a liquid test kit (API sells a good one). Test for ammonia, nitrites, and nitrates.

You’ll want them to read like this:

  • Ammonia (NH3/NH4) 0.0
  • Nitrites (NO2) 0.0
  • Nitrates (NO3) 20ppm or lower.

If you read any ammonia or nitrites that’s a problem. Ammonia doesn’t actually cloudy your water, though. What’s creating the ammonia is one culprit. Excess waste in the tank could be to blame, and the solution is the same. Water changes! Depending on tank size this could mean 25% per week or larger.

So my questions for you are: How big is the tank? How long has it been set up with the turtle in it? How often do you do water changes, and how much water do you take out at a time?

For reference, this is my turtle tank. It’s a 75gal and only has my “little” ~4.5-5” guy in it. I clean it 50% once a month because it has a 70gal canister filter and about 60 gallons of water in it.



This is Yurdle when I first took over his care back in ‘08. You can see what living his entire life without UVB light and in a 20 gallon tank did to his shell.

It could have been a lot worse.

And here we have him today, 5 years later. Even with UVB and a proper diet his shell is still messed up.

So please, give your turtle UVB light and preferably access to unfiltered sunlight.

Did some things.

Water change, then removed the leftover river rock from the bottom. Still a bit of sand (unintentionally added).

I smooshed his plants between the glass and some rocks so he doesn’t kick them around too much.

This tank looks so gross lmfao. But hey, it’s functional. My dream is to have it look really exceptionally nice someday.


Turtulllllle ATTACK!