I have almost like a black powder forming in my turtle tank, what could this be?

I have 2 snaked neck turtles, and recently a black powder like thing is growing behind the large rock in the tank, when we clean the tank and disturb it, the water turns black, not to mention the colour of the water that we have emptied. What could this be? Could it have anything to do with the algae that has begun growing?I have almost like a black powder forming in my turtle tank, what could this be?
Black algae is bad news, but I don't think this is the trouble.





This is dissolving waste and food products where the filter can't circulate water and clean the debris.





It's much better to have open water for your turtles, and either a dock or top/outside basking perch.





I'm glad to see you didn't say it was a ';gelatinous mass';...





This happens to debris not in the water/cleaning flow, and is a bacterial risk to your turtles. They will eat it.





So, your husbandry seems good, and you are cleaning frequently enough.





The only 'cure' for this is to remove the object, or to place it on pedestal-type legs, so water can flow under it. This will occur in any tank, where water can't flow under/around an object, and circulate it to the uptake tube(s) of your filtering system.





Keeping live feeders (rosy minnows, guppies, and the occasion gold fish) in the tank will help with this also. It's good for the turtles' diet, and the fish will graze the floor of the tank until eaten.





If one is lucky enough to get too large to be eaten? Name it, and say ';thank you.';





';Thank you's'; happen rarely, but I do have a few. For some reason? The turtles would NOT eat them, and they got too large to eat.





They will eat what the turtles do not, and help clean the tank.





Enjoy your pets, and I hope this was helpful.I have almost like a black powder forming in my turtle tank, what could this be?
The turtle needs roughly 60% land and 40% water. Once the turtle has out grown it's land area (in captivity) they utilize the water as a place to do their business and this eventually dries to a black powdery substance as you described. They use one particular spot in the water to do this, thus the build up of algae. You could try expanding the land turtles need to sun-bake and putting a water conditioner into the new water, you could also speak to your local pet shop for more advice. If the turtles start to smell bad, use a soft tooth brush to gently clean away the build up of algae on them.
I used to get that. Clean the water more often. It's a combo of dirt, fungus, algae, that just sits in the tank where the water doesn't move much.