I think one of my two RES seems to have a problem with its sight. It's eyes are open constantly and don't look swollen or cloudy, but it can't seem to see food in front of it or around it. It used to be extremely greedy and active before this, always grabbing food faster than the other RES. But it has been less active in recent days, swims less, is largely unaware of food unless it smells it I think. It usually responds to me by pawing at the walls of the tank when it sees me, but it doesn't anymore. It continues to come up to bask now and then, but seems less aware when I come into the room or go near - it usually jumps off when I go too near.
The only thing that happened in recent days was that the filter became clogged with dirt and stopped working for around 3 days, and I had to change the inner filter. Could the sight problem might be an issue of ammonia and waste build up? I just changed the water and the filter couple of hours ago, but the RES condition hasn't seemed to improved.
Tank set-up is alright, there is UVB lamp and basking dock, temperature of water seems fine too. The RES are almost 2 years old with shells 2 inches long.
Is my RES okay? Is it contagious? Is there anything I can do to help it? I would really appreciate any advice!
