Lazy?

[iamjaxraah]

My delta tail, Chevy lives in a 5.5 gallon tank with some other fish. I bought 3 guppies on saturday and he already lived with a silver lyretail molly and a really old guppy. I also installed a heater in the tank. On Tuesday (yesterday) I started to notice some changes:
-some (not a lot) brown algae in the tank
-Chevy hides in the two homes in my tank all the time and only comes out to eat.
-Chevy is not flaring and his tail seems smaller
-Chevy seems a bit pale

SO, I have a few solutions I can put into effect:
1. I can move Jonah [the betta in my 2.5 gallon tank] into the 5.5 gallon tank and put Chevy where Jonah lives.
2. I can clean the tank and see what happens
3. I can freak out and ask someone to help me.

[Littlebittyfish]

Your tank is overstocked. A 5.5 gallon is only big enough for 1 betta or at the very most 2 bettas (tank divided).
The diatom algae may be happening because of the added bioload and ammonia...Your betta is probably acting differently because the high ammonia and poor water quality, which could be the cause of the shrinking fin (finrot). I would do a 50% water change with really good substrate vacuuming and plan on upgrading to a bigger tank eventually. atleast a 10 gallon.
For now, I would start treatment on the finrot. Put your betta in the cup he came in or another container and float him in the tank so that he can keep warm..Premix some aquarium salt in a gallon jug 1 tsp per gallon and do 100% water changes daily on the cup for 7-10 days.

He could also be biting his own fins from stress, or the guppies could be biting his fins...do you have any photos of his fins?

[iamjaxraah]

okay, thanks so much! I feel like an asshole for overstocking my tank, and I have no room for a 10 gallon tank, which is why I have the 5.5 gallon one in the first place.. I'm not really sure what to do about that. But otherwise everything else you told me I will do the second I send this reply. Thanks again for your help!