Fin Rot?

Question
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Followup To
Question -
Ammonia & Nitrite...0, pH....7.6. I have 3 long finned black skirted tetras. ( along with 2 dwarf gouramis.) Water temp is a steady 78. Recently one of the tetras lost color on his dorsal fin & anal fin. Both fins appear to have split between the rays(?). His tail isn't the nice delta shape it used to be. He eats fine & swims fine, even chasing the other tetras. (returning the favor.)  All the other fish are fine. I have no idea how old these fish are, and I've only started this hobby about 6 weeks ago. I do have an extra tank all ready to use as a hospital tank & just bought some Melafix. I realize that w/o pictures it's hard to diagnose this, but any help will be greatly appreciated. On a side note....I bought a Master water testing kit & it has 2 tests for pH...a low & a high. I do have well water that is filtered & softened. (The Hardness was in the 0-50 ppm range.) How do I know which one to use?   Thanks, Dan Gilmore
Answer -
Hi Dan;

How big is the tank?
What kind of filter system?

Chris


 The tank is a 10 gal & the filter is a hang on the back style . Tetra/Whisper brand . Takes the cartridge style filters with carbon.

Answer
Hi Dan;

The hospital tank is a good idea. Go ahead and move him there and use the Melafix. It is an excellent product.

The tank has just gone through a break-in period if it is new. This can cause a lot of stress to the fish and leave them with infections. Make regaular maintenance water changes of 25% every two weeks to keep things in good shape.

Followups welcome.

At Your Service;
Chris Robbins