Please help are my pygmy corys sick?

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xander

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I posted this View topic - Pygmy corys not looking well.• Forum • PlanetCatfish
on Planet Catfish a few days ago and got no response. Can anyone here help me?

I have four pygmy corys in a 30 gallon tank housed with 3 rubbernose plecos and 7 green fire tetras. I have eco complete as the substrate with some dark driftwood and a piece of slate. The tank has been set up for almost a month. I skipped starting a cycle by having the intended filter (eheim ecco 2234) run on my 125 for a few months before starting this 30 gallon. I started it with a few baby swords and what I'm guessing might be "star" something (fast growing hygro sort of plant). I put the rubbernose which I got at a LFS and the pygmy corys from another 30 gallon tank in on the day I set it up. In the previous tank they always hid from view. In this tank as soon as they settled they were all over the tank. Up and down and all around chasing each other around. It seemed like they were very happy in this setup. Well about a week ago I did a 20% PWC and installed a sponge prefilter onto the intake of the ecco 2234. After that they corys seemed to have trouble swimming where they want to. They will swim in spirals and when at rest tend to be on their backs. I thought it was odd that all 4 would do this. At first I assumed some sort of swim bladder problem since they seem fine other than the way they get around. No wounds or missing appendages. I recently did another PWC and put a few peas in there for them to eat. There is no improvement on their motor skills. The other fish seem fine. The green fire tetras I put in from my 125 are happier than ever in this 30 and the males are showing breeding colors. My KH is 4, the GH is 7, nitrates are less than 10, no ammonia or nitrites. The pH was hard to read but I am thinking it's around 7 if not its at least stable. I don't know what to do. My water quality is good and the corys are still eating but I'm worried. It can't be good to just be laying on their backs and running into stuff when they try to get somewhere. Any suggestions?
 
that sucks... i have a herd of these guys and never noticed any of that behavior besides the chasing each other around in a new tank... i would keep your water changes to about 30-40%... i have noticed large water changes having different effects on plants and fish at times.. good luck man, pygmy corys are one of my favorite fish.
 
Was the Sponge pre-filter an actual "Aquarium sponge prefilter" that you purchased? Or was it just a sponge that you put over the intake.

Unless this sponge is absolutely necessary to the survival of something in your tank, I'd try taking it out immediately and then doing a water change.

Either:

A - The sponge is leeching something into the tank.
B - The cories thought the sponge would make a neat snack and accidentally tried to eat some of it.
 
the sponge is made by ATI. It's called "filtermax pre filter". I rinsed it in some of the tanks water I took out when I did a PWC that time. I they do have some sort of blockage would it not pass over time? They still have trouble moving around but seem well otherwise. I guess I'll just have to watch this tank closely and keep up on the PWC. I'll do 10 gallon water changes here on out.
 
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