Cory Cat resurection. (he is a tough bugger) but needs help.

[driver]

I have two small albino cory cats in a 30g planted. I have had them about 4 weeks. They have been fine until last week. I noticed one of them laying upside down on the bottom of the tank but still breathing. So i immediately moved him to the hospital tank with fresh water and treated with melafix (because I was unsure of what I was treating). By the next morning him was swimming around a bit, and the day after he was normal. So I monitored him for 2 more days and then back into the main tank after a 75% water change the day prior.
He did fine for 2 days and then I did not see him and he was floating on top of the water. So.. back to the hospital tank. And he is swimming around fine as we speak. (While he was in the main tank again I did lose a Honey red Gourami that I had for a week.symptoms were lethargy, not eating, slight bloating. And died in the hospital tank.)

I can not determined any symptoms with the cory other than looking like he is dead. Breathing is light. no spots, bloating, gills issues. etc

All of the other fish in the tank are acting just fine.

The only major change in the tank was, that I added a DIY CO2 tank.

I aerate at night, and change the water every two weeks.
Water parameters:
Nitrite 0ppm
Nitrate 5ppm
Ammonia 0ppm
Ph 7.5 (main tank) 7.6 (hospital)

Tank mates:
4 Silver Hatchets
2 Zebra Danios
1 German Blue Ram
2 Albino Cory Cats
4 Cardinal Tetras
3 Rummy nose tetras
1 deceased Honey Red Gourami

any help would be appreciated. I want to get him back to his buddies:ssad:

[doug z]

How long do you aerate at night?

How many plants in the main?

What are you feeding them?

Can you get more corys of the same species?

What is the gh and kh of both tanks?

[driver]

I aerate for 6 hours every night

I have 1 large Amazon Sword 1 Small amazon sword. A couple of jungle val. A cabomba and a big bunch of rotala.

I feed them tropical wafers, shrimp pellets, and what ever tropical flake that make it to the bottom.

Yes I believe the LFS has more of them.

The GH and KH are high. it maxes out my testers. My tap water reads the same on my testers.

I do have a large chunk of african mopani wood and a medium piece of standard driftwood.

I do have a bit of brown algae starting to pop up also.

[doug z]

Corys (and the rest of your fish, besides the danios) like low GH and kH..

Have you ever considered putting some peat in your filter?

Can you increase the aeration time?

You're using dechlorinator with each WC, right?

How long has the tank been set up?

Did you drip acclimate all the fish?

What's the water temp?

[PostalPenguin]

Since he is fine in the hospital tank but doing poorly in the main tank means that the problem is something in the main tank that is not in the hospital tank. Its probably not the GH or KH since that will be the same, the food is the same, are the temps the same? Anything you do differently in the main tank than the hospital tank is where to start looking.

Try turning off the CO2 for a few days and see if he does fine. I would think corys would be fine with more CO2 since they would just dart to the surface more but perhaps he is not liking it.

[driver]

Corys (and the rest of your fish, besides the danios) like low GH and kH..

Have you ever considered putting some peat in your filter?

Can you increase the aeration time?

You're using dechlorinator with each WC, right?

How long has the tank been set up?

Did you drip acclimate all the fish?

What's the water temp?

I would like to lower the GH and KH, but like Postal said the hardness is the same in both tanks. So I wouldn't think that would be it.

I will try more aeration.

I always use a chlorine remover

the temp in the main tank is around 80 and the hospital is about 83 not much difference.

The only differences in the two tanks are plants, CO2, and 24hr aeration.

I just find it odd that the other cory cat is doing just fine, and this one just can take that tank.

i will try a WC and remove CO2 tomorrow.

[doug z]

That temp is pretty high..

All fish adapt to a surprizing degree, but note that genetically speaking it is BEST to stay within the parameters of their original habitat..

Why so high?

You could bring it GRADUALLY (over the course of several days) to 72-76 with no ill effects, and I bet the fish AND plants would appreciate it..

The higher the temp, the less oxygen content in the water..