Feeding up corydoras

So I did something a bit controversial. Still an advice would be appreciated.
At first the idea was to move my sterbais from the main tank in a trio to a separate tank for breeding. However when I visited a recent fish store I noticed that they are selling sterbais in basically the same size as I have, and those sold are juveniles. This lead me to realizing mine didnt do much growing and most likely are not getting fed enough. I have a mixed group of 13, some I have had for year and 8 months, some I have had only for 8 months. However they are around 3 cm, 3,5 cm the larger ones.
I decided to move them to a much much smaller tank (and yes, I know, too small for them), to feed them up, to get them going and ensure their diet is good for a while and controlled to look at them closely.

My question is, how long can I keep them in this too small tank, and how much should I really feed them to not do some damage.

The tank dimensions are 40x40x40 cm. It is established and since the picture was taken I added a large clump of moss on top of the coconut, I also added a bunch of oak/beech leaves to the tank.

For now I have fed once or twice a day and plan to do a water change every 4 days just to ensure the tank is clean. I fed live bloodworms, frozen ones, frozen mosquito larvae, dennerle crustagran, spirulina tablets (to ensure it is not too high protein).
I also have frozen tubiflex, bbs, cyclops, and dry fluval bug bites

If you are trying to feed the fish up, you should feed them 3-5 times a day using a variety of dry, frozen and live foods.

You should also do big water changes and gravel clean the substrate every day or two to keep the tank clean due to the extra food.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.

Never overfeed fish to increase their size. It probably won't. Size is a matter of genetics primarily, and while some fish may get larger, others will not. Multiple feeding for purposes like raising fry, or spawning, is a very different thing. But never to get larger fish.

On the genetics, this species (Corydoras sterbai) is now commercially raised. The ones we see here in NA are from SE Asia, don't know where yours may come from. But they have been commercially inbred for many years now, and many of us know what that means. Enjoy them, be glad they are healthy (assume they are), but don't harm them with too much food. It is detrimental. We all know what overeating does to humans...it does not increase out height. Works the same here too.

I initially wanted to move them separately to feed them up to breed, but then I figured with the size they are at, that will not happen for at least a year.
Both batch are from CZ breeders, one commercial, one private. They are popular here, breed fairly well.

I do not want to make them fat fast like goose, but I wanted to make sure for a while they get all the food I am providing and to teach myself how much they actually need/eat and to try to adjust the feeding in the main tank.
I think I will need to start looking into importing foods like repashy, because my approach in main tank, to drop a cube first of small food (cyclops, bbs, daphnia) or dry and then drop a cube of the food I intent to fall for the bottom fish, like mosquito larvae, bloodworms or tubiflex, is not working as expected. The rummynose are savage and dont follow my division. Ofcourse I could feed dry that falls to the bottom, but that is just not as good, so once I learn what they eat like better, I will look into feeding more in the night or making the repashy gel solutions or something

Beastije said:

I initially wanted to move them separately to feed them up to breed, but then I figured with the size they are at, that will not happen for at least a year.
Both batch are from CZ breeders, one commercial, one private. They are popular here, breed fairly well.

I do not want to make them fat fast like goose, but I wanted to make sure for a while they get all the food I am providing and to teach myself how much they actually need/eat and to try to adjust the feeding in the main tank.
I think I will need to start looking into importing foods like repashy, because my approach in main tank, to drop a cube first of small food (cyclops, bbs, daphnia) or dry and then drop a cube of the food I intent to fall for the bottom fish, like mosquito larvae, bloodworms or tubiflex, is not working as expected. The rummynose are savage and dont follow my division. Ofcourse I could feed dry that falls to the bottom, but that is just not as good, so once I learn what they eat like better, I will look into feeding more in the night or making the repashy gel solutions or something

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You may need to look at better foods, especially for the cories. Bloodworms and tubifex are not in that category. And I cannot agree that prepared/dry foods assuming they are the better quality foods are not better than anything else. It takes a lot of variety or the right live foods to provide good nutrition, but quality prepared foods have all the necessary nutrition.

I know we have had this discussion regarding feeding before and you recommended fluval bug bites, dennerle crustagran. Sadly Omega is not available here at all
What other brands are good for corydoras according to your experience?
I also have hikari cichlid gold balls, those seems sort of nice, hikari is a hit and miss. I have an option to purchase repashy, but not soilent, not available in europe anymore. community, grub pie, igapo, morning wood, super green, those are available here.
I also heard EBO might be a good option for corydoras. Lot of people here use S.A.K., but that is a czech brand afaik. Or Vitalis ?

I feed mostly frozen and live (bbs, mosquito larvae, even had live bloodworms few times) but every other day I used dried (the bug bites, dennerle, hikari) and I use vegetables weekly and twice a week spirulina or nettle wafers.

Beastije said:

I know we have had this discussion regarding feeding before and you recommended fluval bug bites, dennerle crustagran. Sadly Omega is not available here at all
What other brands are good for corydoras according to your experience?
I also have hikari cichlid gold balls, those seems sort of nice, hikari is a hit and miss. I have an option to purchase repashy, but not soilent, not available in europe anymore. community, grub pie, igapo, morning wood, super green, those are available here.
I also heard EBO might be a good option for corydoras. Lot of people here use S.A.K., but that is a czech brand afaik. Or Vitalis ?

I feed mostly frozen and live (bbs, mosquito larvae, even had live bloodworms few times) but every other day I used dried (the bug bites, dennerle, hikari) and I use vegetables weekly and twice a week spirulina or nettle wafers.

Click to expand...

The way I choose fish foods is looking at the first five ingredients. Those will be the predominant ingredients. Avoid anything that uses meals. Fish meal, shrimp meal. That's the tails and heads and the parts that we humans don't eat. You want whole ingredients. Try to avoid terrestrial grains like wheat and rice as much as possible. Fish's digestive systems aren't designed for those. It's impossible to avoid grains in fish foods because they have to use something to bind the ingredients. But try to find something that only has one or two grains in the first five ingredients.

The foods I feed my fish are New Life Spectrum Flakes. Those have these ingredients.
Whole Antarctic Krill, Giant Squid, Whole Wheat Flour, Whole Menhaden Fish, Garlic, Omega-3 Fish Oil, Ulva Seaweed, Chlorella Seaweed, Wakame Seaweed, Kelp, Ginger, Astaxanthin, Spirulina, Marigold, Capsanthin, Zeaxanthin, Eucheuma cottonii Seaweed, Spinosum Seaweed, Chondrus crispus Seaweed, Bentonite Clay, Sea Salt, Naturox (a preservative) used, Krill vacuum preserved

Fluval Bug Bites
Black soldier fly larvae, salmon, fish protein concentrate, green peas, potato, wheat, dicalcium phosphate, calcium carbonate, DL-methionine, lecithin, choline chloride, L-lysine, vitamin E supplement, biotin, niacin, calcium L-ascorbyl-2-monophosphate, marigold extract, zinc oxide, manganous oxide, D-calcium pantothenate, vitamin B12 supplement, beta-carotene, rosemary extract, riboflavin, copper sulfate, pyridoxine hydrochloride, thiamine mononitrate, inositol, folic acid, vitamin A supplement, calcium iodate, sodium selenite, vitamin D3 supplement.

The great thing about Bug Bites is that you don't see a lot of fish foods using insects as an ingredient base. There are some out there like Repashy. But not enough. Because in nature, insects are a staple in many fish's diets.

And Omega One
Salmon, Wheat Germ Meal, Shrimp, Wheat Flour, Pea Protein, Whole Herring, Wheat Gluten, Herring Oil, Dried Kelp, Vitamins (L-Ascorbyl-2-Polyphospate, Vitamin E Supplement, Niacin Supplement, Inositol, Vitamin A Supplement, Riboflavin Supplement, Vitamin B12 Supplement), Citric Acid, Vinegar, Mixed Tocopherols, Rosemary Extract, Astaxanthin, Canthanxanthin.

This is just to give you an idea what to look for. Here's examples on the other side. Without naming any names, here's the ingredients of a food I would not feed my fish.

Fish Meal, Dried Yeast, Ground Brown Rice, Shrimp Meal, Spirulina, Wheat Gluten, Dried Fish Protein Digest, Potato Protein, Feeding Oat Meal, Soybean Oil, Fish Oil, Sorbitol, Lecithin, Algae Meal, Inulin, Beta-Carotene, Monocalcium Phosphate, Freshwater Shrimp, Vitamins (Ascorbic Acid, Inositol, Niacin, Riboflavin-5-Phosphate, D-Calcium Panthothenate, A-Tocopherol-Acetate, Thiamine Mononitrate, Vitamin A Palmitate

Or this...
Fish meal, wheat flour, brewers yeast, Ca-caseinate, Hermetia (4%), gammarus, spirulina, sea algae, mannan oligosaccharides, cod-liver oil (containing 34% omega fatty acids), herbs, alfalfa, stinging nettle, parsley, paprika, green-lipped mussel, spinach, carrots, Haematococcus algae, garlic.

I don't even know what Ca-caseinate is.

I hope this gives you an idea of what to look for.

Agree, look at the ingredients. And, know what the fish naturally feed on in the habitat. For example, cories eat insects, insect larbae and crustaceans. Probably worms, but the first three are without wquestion the primary food according to examination of the stomach contents of wild cories. Do not feed any herbivorous foods, like algae/spirulina, vegetables, because they cannot digest these. Their mouths are a clue here, because cories do not have teeth so they cannot possibly graze/scrape algae, etc, or vegetables.

Keep proteins low. The bug bites have protein in the 30's, that is plenty. Foods higher in protein can cause deposits, the white bumps sometimes seen. This is where most all flake food is unsuitable for cories, too high protein level.