HI Guys! I currently have a 15 gallon/60 liters long aquarium rumming and I have doubts regarding stocking. Right now I have 2 cockatoo cichlids (apistos), 1 bristlenose pleco and a dwarf crayfish. Is this stocked correctly? Can I add more fishes?
Even though a site like seriously fish advice to keep bristlenoses in a tank with the base dimensions 60 x 30 (23.6 x 11.8), a lot of other sites suggest something like 25 - 30 gallon. I've kept one myself in a 30 gallon long and it definitely used all the space. To me the bristlenose does not belong in a 15 gallon.
For the pair of apistos I'd suggest something like 20 gallons as a minimum - though again there are sites that suggest 15 gallons. When it comes to the dwarf crayfish I don't know much, but 15 gallons is definitely enough space for it, however I don't know if you're running the risk of it getting eaten or the crayfish eating some other fish.
I'd say that since you have both the apistos and the bristlenose in a tank that's slightly too small, I wouldn't add anything else. Especially not when the apistos are semi-aggressive.
Unless it looks fluffy or in other ways "odd", it's just their natural coloration. It changes a little from time to time and can be caused by stress, change in environment, temperature, etc. Usually nothing to worry about.