Fish disease??

Question
Hi! If you could answer this it would be greatly appreciated!
Sorry but i'm not exactly great with fish- i know i have 3 bala sharks (3 years
old), 1 angelfish (4 years) and 3 bristlenose (2 months), but i'm unsure about
the other species, they're small, roundish and have thick vertical stripes on a
silver body with bright orange fins below the belly (6 months). I have real
plants, and I used to have a snail which recently died. My tanks about
60X50X30 cm, and i've had it for almost 9 years now, but the filter is quite
new.
About a couple of months ago a couple of this 'x' species fish began
swimming vertically, tail up. I thought at first it was some wierd mating
behaviour, because they still come up to feed, swimming normally for a while
before returning to this position. Eventually the whole species swam this way
a couple of weeks ago. Today i noticed one of my sharks doing it too, so im
worried its some infectious disease. It also appeared to have a slightly
swollen belly. I've heard about swimbladder problems but im still unsure
about what it is. If you can please give any suggestions about what it is and
how to treat it that would be wonderful!
Thankyou


Answer
While I do not know what kind of fish you have, I do not know of any fish that would have this behavior, especially since it is spreading to the other fish. As you mentioned, the first thought that came to mind was either a bladder problem or an internal parasite. Considering it has spread, I suggest getting an all-in-one internal parasite and disease treatment and treating them. Also, give them some romaine lettuce, as this sometimes helps to relieve the bladder probems if that is the problem, its also good for them. Just get a veggie clip at your local pet store and clip a few leaves of romaine and put it in the water. Also, when you treat be sure to follow the directions exactly including water changes and dosage. I hope this helps. Let me know if you need anything else.