If you treat for Columnaris now it won't hurt a thing. That bacteria is the devil I just lost a male crown tail and a female to it before I realized what it was! I thought the male had swim bladder :( He ended up with an ulcer below his gills and a white "string" coming out all within 24 hours! Go ahead and treat with tetracyclin or erythromycin. I used this and a combination of Jungle Fungus to treat a female I picked up at Wal Mart with bad fin rot and the same white cloudy patches and she's doing great now (looks like a different fish). I also just treated a female who actually did have swim bladder with epsom salt, she's doing fine in the sorority, the symptoms were quite different she had full energy just couldn't keep herself under water.
I'm sorry, but my almost two decades of experience with fish is saying that this girl needs anything but harsh medicinal treatments such as that. She has had no prior illnesses, has been in a cup for a long time, longer then most at the stores, has been given clean water every day. Doing the medication on her will do more harm then any good.
Larsa, how many days has it been since you noticed the fluffy stuff on Kasumi? Have you noticed the fluffy stuff spreading rapidly? In columnaris, the cottony patches will grow and spread quite quickly. Also, the patches don't tend to fall off. There are other symptoms that definitely identify columnaris and fortunately, Kasumi isn't displaying any of them. I think Myates is right, Kasumi is simply rather stressed right now.
I don't believe you need to medicate her. Just as in humans, too much medication can be detrimental. It will cause the fish to become resistant to the medication so any further treatment will be ineffective. Truly, I think Kasumi and the other girls are okay, just stressed. Go ahead and return them to their big sorority tank. They'll be just fine and I think you will find their behavior will improve once they have some space to swim in.
lol yeah XD That day I got the first few posts, I added her back home with her sisters. She and her sissies like freaked out at their home's makeover with all the new plants and rocks. Surprise for them! :3 At first she hid and stayed at the bottom for a while, but the next day she was totally normal and hyper again! I think maybe she was just shedding her slime coat and wanted to go home :P After I put her in her clean water the slimy fuzzy stuff went away and I have not seen anything in over a week. I didnt even use AQ salt on her ^-^ Shes playing right now, inspecting a rock- trying to hunt for food 0.0 pecking around the tank. LOLz She like to jump up and bit my finger again too so I know shes happy and healthy! Im gonna keep a good eye on her, b shes ok now! :D thank you guys so much for your concern, I really appreciate it!
Glad to hear she's doing better and they are back in their homes :)
Sometimes, not doing anything can help more then doing too much of something. :)
Best of wishes and hope they stay happy and healthy for years to come for you.