Guppy Disease Question

Question
We have had 3 guppies in a 4 gallon tank (baby BiOrb tank with canister
filtration) for more than 6 months. About 3 weeks ago ) 1 of them developed
what looks like tiny bubbles under the skin of its dorsal fin. The scales at the
base of the skin are enlarged as well. The fish swims but seems to struggle to
stay horizontal while swimming. The other guppies are not effected. I treated
the tank with Maracyn-TC but it has not helped. I cannot seem to find what
the cause is and am eager to help the sick fish.

Answer
Hi Michelle,

Do you have an additional external canister filter?  BiOrbs come with internal filters (which are not canisters) and frankly do not do a very good job.  Have you tested your tank water for ammonia, nitrite and nitrates?  99% of the time the key to disease problems lies with these results.

Honestly, as pretty as BiOrbs are, they are really glorified fish bowls and are awful for fishkeeping.  Heaters never seem to fit properly in them, the built in filtration is terrible and expensive to constantly change cartridges for and it's impossible to get in between all of those ceramic rocks to clean thoroughly enough.

Maracyn TC is for bacterial infections that are gram negative.  It may be better to try Maracyn II as it seems to be a little more effective against internal bacterial diseases.  It wouldn't hurt to feed an anti-bacterial food and use some Melafix.  This could be the first of many illnesses until you know what your ammonia, nitrites and nitrates are.

Good luck : ) April M.