Diagnosis - Guppies

I've had my guppies in my tank now for around 2 months or so. I've lost a couple a few days after acclimating, which I put down to excess stress and too much lab breeding defects.

Anyways, many weeks down the line, I've lost another (one of the original 5 (I did a 5-5-5 additions) so been in the longest). Wasn't showing any kind of symptoms, feeding fine, joining in with the rest. Inspection of the body the only thing I could see strange was his lack of rear fin.

This seems to have sparked something with another (both cobra), he has gotten worse over last 2 days - lack of activity, as if he is constantly exhausted. Minimal fin movement. Yesterday I found him curved over to one side, lying on the bottom and I thought he had passed....nope, he's just there, curved over, not moving unless he has to, looking like he is gasping. (further inspection I can see the same issue with the rear fin)

Then today, around 4 hours ago, I've spotted that one of my yellow guppies is having fin trouble, he still had it, but it now looking like he can't move it, he is swimming strangely (usually more vertical or on his side) and the fin looks like its clumped together, not the usual shimmery style we love them for.

My thoughts are potentially Columnaris or Fin Rot - what does the community think?

I'd love to try and save these two, but I fear the worst for them .

Setup:

125L Fluval Roma with external canister filter. Fully cycled (0/0/20).

Tankmates - All guppies. was 15 in total, now 14 (2 sick). The other 12 do not show any kind of problems similar to these whatsoever.

TIA,

James

(NB: I'll do my best to get pics)

 

Just curious what are you using for testing? Fin rot and even clamped fins are usually brought on by bad water conditions. Is there gray areas at the ends of the fins that appear to be disappearing? Is there fuzzy stuff at the fin? Pics when you can get them would be helpful

 

I'm using the API master test kit. Although I haven't checked it in a couple days, but I did a 40% water change 3 days ago.

I have to say though, some of the others do certainly have disappearing tail ends (well, I would say going see-through?). Others do have greying. No fuzzy stuff on the fins though that I can tell. It only appears to be affecting the tail fins.

 

Hmmm, interestingly my PH, which I haven't checked in a while, it up around 8.2 :S. I shall have to re-check my tap water again to see if this has changed.

 

Re-checked. I think it's going to be my PH. For some reason in the tank its at about 8.2, where as my tap water is around 7.4. My other parameters are all fine, re-checked and they are indeed 0/0/15-20.

 

Could be PH but usually it would have to be higher than that. But maybe if doing large changes could be PH shock causing the stress of the fish.