Sorry in advance for a long post, but I know giving information sometimes helps with answers.
I keep about 15 or so albino corys in a 29 gallon and have raised them off-and-on for years, but have sometimes had difficulty with retention rates. The fry seem to do OK for 2 or so weeks then seem to die off (sometimes, but sometimes not).
I do not feed BBS or Microworms, nor is it really an option for a lot of reasons. Please don't debate me on this, as I know it would be much better for the fry, but it is not going to happen.
I know these fry can be raised with dry-type foods as I have done it, sometimes with about an 80% retention rate. Sometimes not. FYI, I use an anti-fungus until the fry are hatched.
I have tried the Hikari First Bites, but with some problems. I have used the Golden Pearls, usually in the 50 to 100 micron size, and occasionally used the same in the 05 to 50 micron size. With any of these foods, I place a small amount in a teaspoon, add some of the tank water to it, then use a small dropper to place in in the bottom of the tank. I typically start off with a 2.5 gallon, after a few days move them to a 5 gallon, and after a few weeks (2 or 3) move them to a 20 gallon long for grow-out. Also, I keep 5 or so ramshorn snails in the tank to clean up any waste food, etc. I move them when I think overcrowding is a problem, or they are dying off, which is the heart of the issue.
About the 3rd week of June I had a batch of about 100 to 200 hatch. The problem was that I was leaving on vacation for a week. I used a turkey baster, got some muck out of the filter, and added it for the newly hatched fry. I also placed some fry in the back of a Whisper filter, a trick I had used previously (successfully). Another person came in once and added some plankton flake (simply crushed it up). When I got home many were still OK. I moved them to the 20 gallon, fed them mostly the 50 to 100 golden pearls, and I guess I have about 50 to 60 % left and they are now about 1/2 inch. I usually don't have any problems once they are that size.
Meanwhile, when I returned home, I had about 250 eggs, which I pulled and placed in a 2.5 gallon. The fry hatched, and after a couple days I moved them to a 5 gallon bare bottom since there were so many of them. I started them off with the 50 to 100 golden pearls again, and they seemed to be doing very well for about two weeks. Maybe I would lose 5 or so a day. That increased to about 10 or more, and bottom line, I have now lost them all. I think the bottom of the tank was clean.
When batch number 2 hatched, I had another 200 or so eggs (batch #3), (believe it or not). I placed them in a 2.5 gallon, thinking I finally had this figured out. They hatched and I guess I have about 150 or so now. They are about 2 weeks old, getting overcrowded so I plan to move them tonight. My concern is I will begin losing them within the next week or so in the 5 gallon (like with batch #2). I think I will take them straight to the 20 gallon, maybe because I had better luck with it on batch #1.
Again, sorry for the long email, and finally here are my questions:
1) Are any of you raising cory fry with dry food only, and if so, what are you using and how are you feeding it? I have heard that some of that type food will expand once consumed and bloats fry causing them to die. If that is true, it has not consistently been my experience.
2) Are you letting it soak before feeding for long, maybe 1/2 hour?
3) What fry to tank ratio do you keep for the larger harvests, and up to what size?
4) How (and do you) keep the bottom of your tanks clean? I switch between thinking I should try to keep it clean versus stuff on the bottom gives them more muck to eat? Obviously the snails leave their waste, and I try to remove it.
5) Do you have any other suggestions for food without going to the live foods? Any other dry-type products that would be available? And how would you suggest feeding it?
I would like to try other corys, but have vowed not to seriously start until I have this down pat.
Thanks in advance for taking the time to read this and for any support.