Hi there 3 weeks ago I cam back from vacation to find that my tank looked like it has been through a shelling. There was white stuff everywhere and my 2 angel fish one was on the ground the other one was fine on the weekend I saw that there were these white stuff with tentacles all over the tank and I freaked out and we changed the water we then also found it had worms in it so we throughout all the gravel. My husband told me that the black fish had fin rot and that he medicated it and so the fin rot is over but the fish is on the bottom of the tank on the side of the broken fin and when I lifted it up now to make sure it was eating and to have a look at the fin the fin looks like a mermaid split tail fin like you see in disney movies. The tank is on 30c and it's being medicated with just general anti-everything medication every week or so (the first 2 weeks it was more often to kill the disease) will it heal??? will the fish go back to normal?
I think the fin will heal. My friend seems to use something called melafix when he see's fin damage like you describe.
The white worms sound like planaria.
White stuff with 'tentacles' sounds suspiciously like hydra?
If both of these were present, then it 'might' be that they were overfed perhaps for the holiday period? (not saying this is so, its just a possible cause), and the gravel (as was), may have needed a good substrate cleaning prior to the vacation anyway?
I note you say you've 'throughout' threw out? your gravel? so i'm presuming you may have overreacted a bit in the panic and potentially 'may' have disrupted the good bacteria that is living in the gravel aswell, this will in turn force alot of extra load onto the actual aquarium filter, and your aquarium will quite probably go through a mini cycle.
I can relate to the panic though.
You are medicating the tank, but i'd still do all water testing for ammonia, nitrite, Nitrate and PH anyway regardless if only so you know the levels are not contributing to any continuing symptoms. While treating the tank your husband may well have removed all traces of carbon in his filter(s) while medicating it so check definitely for ammonia spikes even in established tanks. You need to ensure you deal with ammonia spikes effectively as this can cause further issues going forward.
Nightmare I know, totally sympathise, but its not unrecoverable. with good care now, i'm sure you can turn this right around.