"his rear fins and very frayed, could this be a side effect of the freshwater dip?"
Not a chance, that is called "fin rot" which is a bacterial infection due to poor water quality. From what I have seen (my hippo had this coming out of qt
), this is usually due to excess organics (doc
) in the water. Best thing to do is several large (30-40%) water changes with aged (24hrs) sw
over the period of a few days. You can try melafix along with water changes, it seemed to help with my hippo, but other antibiotics I would add only in qt
. But the water changes alone should do the trick. If the white specs return, it may be ich, a parasite which needs to be dealt with in qt
. Fresh water dips only prolong the outcome and do not cure ich, and are stressful to the fish (as you have seen). But the water changes are a must for that type of bacterial issue. I would do 3 large ones, then get on a regular schedule every other week or so. You should see big improvements in a few weeks, he will grow it all back in a month or so of good water quality. Are you running a skimmer on this tank? If you start seeing white specs again, let us know and we will help...