My red male betta has been looking a bit unwell for the past few days.
It hangs around the top of the tank most of the time, swimming much less than it used to.
Tail and fins are looking damaged, some splits and cuts, before it had the occasionaly split or cut but it always grows back quickly, not it's looking more damaged than any of the previous occasions.
Tested the water and everything is ok.
Think it might be a lack of oxygen, since I took out my internal filter on wednesday and so no more air bubbles in the tank, just the external filter, but still plenty of plants to provide oxygen.
Any ideas?
Cheers