Here is my problem: I have a red eared slider turtle in a 55 gallon tank that's 90% full of water. After a 100% water change the water starts turn really foggy and not exactly green but more like a yellowish green. The water smells really bad like rotten eggs. When we first got the tank and set everything up the tank lasted a whole month without developing any sort of overpowering scent and stayed pretty clear most of the time until one day the water just smelled absolutely horrid and I decided to take the filter apart and clean it thoroughly. The process took like 3 hours. The filter was just completely FULL of some green slimy GUNK like LOADS of it.. I'd say 3 pounds of the stuff... It was all over inside the filter tubes as well, basically it was every where inside the filter. I use a filter for a 75G tank on my 55g. Now after I cleaned it thoroughly and added new filter media it started smelling bad and the gunk started to build up in only 2 weeks or so..
Another problem: We are on a budget and can't afford much. We couldn't really even to maintain turtles to optimum, but problem is they were getting sick in the conditions we had them in before and had to make the sacrifice. So please be light on the possible expenses..
Details on my tank:
1. 55 Gallon, 90% full.
2. I use mechanical and bio filter
3. Basking Lamp, no UV
or UVB just a normal lamp to warm up their basking.
4. In tank water heater set to 65F so water remains around 70F-75
5. Turtles are fed in the tank only once. One day yes one day no.
6. There are no rocks or sand in the tank. There is absolutely nothing in the tank besides the water heater and basking spot, and the pump.
7. I tried doing 40% water changes every 2 days after the smell started to develop, but it comes right back within 2-3 days.
We really need to solve this issue soon because we are having guests stay over.. Someone please help.