hi, I recently bought a 42 gallon tank, with 5 goldfish...
I put in some benificial bacterias... and everything is fine with the fishes, but a month later, now...
I've noticed a layer of foams/bubbles started to grow on the top layer of the water... i can't get rid of it... it'll disappear after a water change, but within a day, it is back...
I wonder if the foams are bad for the fish? and what i should do about it?

DO you know your water parameters, like ammonia, nitrates, ph and nitrites? I am not an expert but I bet the people here who are may be able to help you better if you have those numbers. I remember when I was a kid we would get foamy stuff in the tank, but I don't know what it was.

Good luck, I am sure someone here will be able to help you! ;-)

thanks for the reply, I dont have any data on water chemistry... because I'm very tight on money right now... can someone tell me what the foams might be without those data, and a little advise on if it's harmful to my fish?

I have the same thing! I was told not to worry about it, that it happens, and that the fish always seem fine even though its there. Mela-fix can also cause bubblies on the surface.

Im not an expert though, so hopefully someone can come along and help that is!

EDIT: You dont clean anything with soap do you?

Hi ID - could your fish be spawning at all?

Otherwise it could be a build up of contaminants from overfeeding etc.. how often do you do waterchanges?

What kind of beneficial bacteria are you adding? This could be the cause of the bubbles you see.

thanks for all the replies!
no... i dont use soap... hahha. and i'm using Stability to build up the tank, I put a little each time after i change the water... and i change it about once a week, sometimes sooner, because I have little self control on feeding them less! they just seems soooo hungry all the time! hehhehe.
the foams weren't there when they were in their first home, a tiny 10gallon tank... now a 42gallon, and weird foaming...

Since it's a new tank it might not be cycled yet and the foam may be a bacteria bloom. That has happened to me before. It will go away. If there is any way possible to get a test kit it will be very helpful for you to know where you are at in your cycle. How long has the tank been running?

yeah, i think i'll go get those water chemistry kits...
the tank is about 1 month old...

Hmm, maybe thats what happened to me. The bubbles started while I was away and thats when I lost so many fish...

Since your tank is so new I'm guessing it is a bacteria bloom. I used to have my fish in a tub, I got a little over zealous in cleaning it a time or two, threw it into a mini cycle and I would get that foam. Another member explained that it was a bacteria bloom. So not to worry, it will go away as your tank cycles.

thanks everyone... everyone's been so helpful... I believe it is because it's a new tank, and also a bacteria bloom, since one fish got popeye and another got a tail split... i since changed 50% water, and super cleaned my fliter... i didn't realize how dirty it was, maybe that's what caused the weird foaming... thank you for everything! after i cleaned the tank, i took care of the popeye with 2 epsom salt bath and added some melafix and pimafix in the tank... the split tail, i'm still waiting, i'm not sure it'll actually grow back together...