Sometimes, my turtles are not active at all. They appear to be floating on the surface, completely motionless. I generally change water in that case.
However, I also think that not giving them proper ventilation with fresh air and sunlight could also be making them inactive. I am not sure; is it really an issue? If yes, I will have all of them to bask in shaded light near window every day. If no, how should I handle this situation?
Edit: Added more info.
- Light source in aquarium - CFL (compact fluorescent lamp) 8 watts, only one lightbulb.
- Aquarium size is 24 x 36 x 24.5. There is gravel at the bottom of aquarium and some plastic flowers for visual aesthetics. The turtles like to sit on them as well. I don't know how they do, but they can spend hours sitting on them.
- Filter - two submersible filters. They generally like to sit on top of the filter :). Maybe they want to get close to the CFL attached on top of aquarium. Filters looks like this:
One air bubbler - with air stone stripped, so that mosquitoes can't sit on surface and lay eggs.
What kind of turtles they are - I don't know, but you can see pictures in my other question here: Red flesh coming out my turtle's tail