One on my 6" Discus was swimming erratically for at least an hour today. Basically a 45-degree angle, trying to swim down but using allot of effort with little success. Now it seems normal but is hiding in the corner. I cannot detect any swimming issues when it swam out for food.
Is this an issue I should treat with something or just wait and see if it returns?
I was thinking swim bladder but now I’ am not sure.
I have 5 Discus in that tank (75g) - no signs of stress on any of the fish (color) and all the other fish in the tank look ok. Ammonia and Nitrates are very low. Water changes have been on their normal schedule. These fish have been in this tank for 8 weeks. Marine land 450 filter (deep one) was set up with a "dirty" foam block between the filter inserts and one of the two ATI sponges was old. Temp 86F. PH is currently 7.0
The fish has not shown this behavior for 1/2 day now.

