I have sixteen goldfish (comet or feeder types) born this summer to outdoor pond fish. Most doing well -- at present they range in size from 1/4" to 1.25". I am raising them in an indoor tank. Largest fish are very robust. I'm new to raising goldfish.

Problem: two of the mid-sized (1/2") fish began having buoyancy problems, difficulty eating at surface, died after several days although I was able to assist them eating a small amount. Might have had clamped fins and slightly bent spine, difficult to tell at this size. Later stage, fish hang near surface, tail up, but could be roused at feeding time, though they weren't actually able to eat at surface. Some of the other smallest fish might be in early stages of same symptoms. I'm not sure what normal healthy fry look like -- some of these mid-sized fish seem to have reddened areas in the head, not specifically gills. The fish are black / silver at this stage. No obvious signs of parasites.

History: One bout of hemorhagic septicemia which cleared up using "Goldfix". This took place prior to sudden ph crash three weeks ago. All fish recovered. I have since added a ph buffer block, cut back feeding.

What I've suspected / tried: Possible constipation or air swallowing from floating fish flakes. Fed cooked peas alternated with chopped up blood worms (since the fish are so small). Feed later in day when tank is warmer. Costia? Have not treated for this yet. I tried "Goldfix" once again four days ago and added aquarium salt two weeks ago.

Set-up: 8 gal. tank with filter and heater. Smallest four fish in fry net breeder within tank. This tank has been running for several months. All tests fine (ph, ammonia, nitrate). Temp. between 68 and 72 degrees (daily changes slightly due wood-heated cabin). Doing 20% water changes weekly. Use water conditioner with changes.

It could either be due to some internal malformation that isn't apparent, and is now killing off some of the fry, or it could be an internal infection being spread by the crowded conditions.

what are the PH, ammonia and nitrIte levels?

Ph 7.0; ammonia - none; nitrate - <5mg/L; nitrite: not tested.

I know sixteen fish sounds like a lot, however these are mostly about the size of your little fingernail in length. Only two 'large ones'. Two of the smallest seem affected now. (They have just passed the 'spinal cord and eyes only' stage, and didn't seem to grow much over two months. That is why I separated them from the larger fish.

I don't know anything about fry survival rate. Anyone?

I would greatly appreciate some help on this -- am not sure whether to go ahead and treat for bacterial, fungal or parasite condition. Am inclined to do something for 'most likely' scenario, just in case, but don't know what to suspect first. The rate of affected fish seems to be increasing over the past day or two.

I guess I should have mentioned that I'm very, very worried about these little guys... It's breaking my heart to see them suffer.

I've done quite a bit of research and have tried to come up with answers, but there isn't much info on goldfish fry, specifically, so I don't know if this is to be expected due to 'survival of the fittest' or something.

Does anyone know of a site that has fry info? I'm getting a little freaked out and would like to do something for them soon...

Nitrates aren't too important. It's the nitrItes that kill. You really need to get that tested.

Thank you, Shiari. I will get the nitrIte test kit and do it asap.

It was my understanding that since nitrAtes at bad levels become nitrItes, so long as the nitrAte tests were ok, they shouldn't be changing into nitrates. Wrong assumption? I haven't had any bad tests (nitrates).

You've got the cycle backwards.

First you get ammonia from the fish waste. Then bacteria grow that produce nitrItes. Then bacteria grow that use the nitrItes and turn 'em into nitrAtes, which is far less harmful than the previous two.

Oops, you're right. I WAS thinking backwards. I meant the ammonia levels have never indicated any presence of ammonia at all. I've been testing ammonia often and never a trace. So assumed no nitrItes.

Meanwhile, do you think I should be starting a treatment of any kind, just in case?

I have been pretty vigilant about water quality...

I would suggest adding aquarium salt to help them (makes 'em feel better). The measurements go one tablespoon per 5 gallons, so you might try 1 1/2 tablespoons of aquarium salt. It helps them a lot in stressful situations such as with bad water.

You might also try daily 10% water changes. Replace a gallon each day, and every fifth day (after removing a total of 5 gallons of water) re-add the salt.

Don't know what else to do. I hope they end up okay.

Will do a water change and add aquarium salt, tonight, after nitrite test (kit on its way with a friend).

I did add salt a week ago, so will have to do the calculation on this...

Your help is much appreciated - thanks! Will update if I have any news.

Update:

It tested the nitrItes and they were.3 mg/L (N02). I did a 25% water change and will continue with the frequent (10%/day) changes which Sharia suggested and will add salt once I have replaced all of the water and can monitor the dosage.

For five days I've been feeding only blood worms (chopped up very fine, since larger ones get stuck in their mouths quite dramatically) and soaked flakes.

I think the whole problem originated from a combination of constipation and water quality... and perhaps just 'failure to thrive' -- I imagine it's unrealistic for ALL of the fry to survive? There must be a process of natural selection going on here?

The very smallest seem to be growing now that they are separated from the larger ones. I had to raise the fry cage so that the bottom wasn't so deep. The very small fry only seem to bottom feed, seem to prefer algae wafers, and they were having trouble with the deeper water / bouancy since the ph crash.

Anyway, everyone seems to be doing better now. I hope some of this info will help anyone else who is trying to raise goldfish fry...

I will be going over to the tank cycling section soon, as it looks like I will have to borrow a much longer tank, which means figuring out how to move everyone over safely.

Thanks to Sharia for her comments, I appreciate the help!

A lot of fry do die due to deformities, both visible and not. There are also toby fry that eat smaller fry so it's very good to separate the sizes. I'm glad they seem to be improving. When they get big enough to show up, you have to take pictures of them for us to see. ^________^