i did a water change in my 20g, housing , at the time 2 small syn. petricola-dwarf -1-1.5", now the fish constantly swim in circles and chase their tails; they are whacked out or something; no sign of disease, maybe they got caught in the whirlpool when i was refilling the tank??? are they "fried" for life?
My petricolas played pretty constantly at that size, but I never kept them in small groups like that, so I couldn't say if that's necessarily a normal behavior for them. I CAN say I've done some large volume water changes on petricola tanks, to no ill effect, but you might have a higher dissolved gas problem in your local water that I didn't.
I did have one petricola that insisted on chasing itself round and round the outlow for a powerhead. He did it for about 3 weeks, til I'd just about decided I was going to put him into a tank with only a backfilter so I didn't have to watch it anymore. He just suddenly got bored with his game one day and stopped doing it though I wouldn't worry too much, as long as they're eating and otherwise acting normally.
They act like this and then they fall to the bottom of the tank,"lifeless"?? i almost flushed
one, because he didn't seem to move for about 15 minutes after "freaking out". i am wondering if maybe they got caught in the waterflow and maybe got slammed against a rock or something??? i poured the water onto the top of a large cave in order to not disturb the substrate. it's really weird; they have been acting like this, since saturday, BTW
no, but i am this saturday as the water is getting a bit cloudy ; i'm using a sponge filter in that tank and i have no carbon in there yet, so i will need to change the water this weekend.
Does your tank regularly cloud up between water changes? How long has it been set up? I've always seemed to have the clearest water in the tanks with sponge filters, personally.
the tank has been set up for around a month; my other tank in the room is crystal clear? i think that i might have fed them too much?? i feed them at night, before i turn the lights out and the food is gone in the morning though?? when i change the water this time, i will pour the water in more carefully and watch for the little petricolas
Chocky do you have an ammonia and nitrite test kit? If the tank is that young, you might have been having a spike in either of those two levels that were causing problems for the little synos. If your other tank has been up and established for a few months or more, you can supplement bacteria into the new tank, to help speed the process up. I would definitely test them immediately, if it was me.
Like many Tanganyikan fish, S. petricola do not do well with large water changes. My group does the same thing if the changes are too big (30%+). Do smaller water changes more frequently.
I am not sure the exact cause, but a couple things to note:
The fish are from a stable body of water, even an extremely large rainstorm wouldn't have any affect on water chemistry in Lake Tanganyika. The fish are unlikely to have evolved any response to changing water chemistry. A good example of this in another fish is the high mortality in many Cyprinid fry, Barbus spp. in particular, from even small changes in pH and hardness (TDS).
Do you let your water stand for any period of time? Tap water typically contains higher levels of nitrogen gas than water that has sat for several hours (often seen as small bubbles that form on the glass and other surfaces in the tank). These fish are definately less sensitive to large water changes when made from a stock tank and not directly from the tap. Nitrogen narcosus perhaps?
Another thought would be per Barbie's response of ammonia or nitrates, or combinations thereof. Regardless of cause, too large of changes can cause mortality in these fish (and has in my aquariums). More frequent, smaller changes are in order. If the fish were "out of sorts" for more than an hour or so, it sounds like you got lucky this time!
yes, pturley, i got really lucky! the fish were "scrambled" for about 3-5 days, but now are eating and chasing the smaller petricolas that i bought to replace the bigger ones that were wigging out!! i did not change the water on saturday as the fish are doing well, and the water has cleared a bit, but i definitely will be more careful in my petricola/multipunctatus tank! their bellies are nice and round and they seem ok; i need to get more caves for them though
i did a water change in my 20g, housing , at the time 2 small syn. petricola-dwarf -1-1.5", now the fish constantly swim in circles and chase their tails; they are whacked out or something; no sign of disease, maybe they got caught in the whirlpool when i was refilling the tank??? 
are they "fried" for life?
I wouldn't worry too much, as long as they're eating and otherwise acting normally.
