Help! Guppy With Fin Rot (I Think) And Dying.

[cool9854]

OK i know what the admin said and how to get all the pH and stuff and i will I just need help right now.
 
I have a 10 gallon freshwater tank, 81.5 degrees Fahrenheit, with 2 otocinclus catfish, 3 guppy's. I try to do 25% water change every week and 50% every month.
Here is a picture of the infected fish  
 

 

[BaylorPerez]

for a quick but not perm fix, try adding some melafix(all natural) rather than their counterpart the one that seems to had every bad to a fish tank. as i had fin rot and used the melafix and within 30minuters the fins were better. As to why the fin rot is their we need to find the cause. Are any of the fish nipping at the said fishs tail/fins. Also, what are your Ammonia and nitrite/nitrate levels. as this can also cause the fin rot as the fish might of lost its slime coat as to why your seeing this finrot. Also if you have a seperate tank you can put him into it, then monitor his progress with the 1 dose of melafix to both tanks

 

[cowgirluntamed]

You may also want to turn your heater down a bit. 81.5 for a guppy is a bit high. That's at the top of what they say they can handle but they don't like it. I keep my guppy tank at 77(ideal is 77-78). The higher heat may be a stress factor for them. Also the temp for the oto cats should be between 70-78. They won't like it that hot for long either. Fish stress can cause multiple things to start going wrong.  And as what Baylor said, we really do need your ph, ammonia, nitrite, and nitrate levels as this tells us what the fish's living condition is way better and we can help you. Other than ph, high levels of the rest  of these things can harm your fish and cause stress, which in turn will cause illness.