Cherry shrimp are harassing pygmy cories?

A Great Barrier Reef (GBR) fish would die in fresh water. What freshwater fish are you thinking of? Green bar rasbora?

Betta cocchina would eat some shrimp but not bother other fish, even fry. It would take over the driftwood cavern since this is a very weird peaceful betta in that it builds its bubble nests inside caves or crevices in driftwood. You could have a male and one or two females in a ten. I have had three pairs of this betta in a 75 gallon tank with lots of driftwood, a pair of bristlenose plecos, and glowlight danios. All three were spawning and breeding and there were three kinds of fry growing up in the tank with the adults and very few cherry shrimp. If you have that many shrimp in the tank, they will kill themselves too. Remember something about Malthus in science class? Cherry shrimp will ably demonstrate Malthus's gloomy predictions if you don't regularly thin out the tank yourself. Pick out a few of the reddest, nicest cherry shrimp, then remove all the others. Otherwise you will end up with 99 to 100% of the shrimp dead due to overcrowding, and if there are any survivors, they revert to the plain colors of the wild shrimp cherries were developed from. Even with more than 50 bettas of different sizes in that tank I still scooped out cherry shrimp four or five times a month.

After several years, I recently reset that tank and eliminated all of the shrimp (I think).

Is the problem that the cherry shrimp are stressing the Corys or are the Corydoras not getting enough to eat? Knowing their fondness for bbs (baby brine shrimp) they might even take some baby shrimp.

Is there a clear area (or could there be a clear area where you could feed the Corys? Take a small soap-less jar (pickle soaked with baking soda or salsa, etc) and wet a few appropriately sized flakes, take some up in a turkey baster or pipette (dedicated to all things fishy), stick it down into the tank by the clear area & gently release a few flakes. Corys don't have very good vision though their whiskers are very sensitive (taste/feel/smell?) Once they become accustomed to feeding in that spot they should check it out more often.

I lost some cherry shrimp, perhaps by feeding them crumbled regular flake food. A Rhonda Wilson plant column in TFH (Tropical Fish Hobbyist) magazine suggested that a high animal protein diet (as opposed to algae & plant protein) can weaken their shell and that sometimes molting doesn't work out so well for them. So feed the Corys a little at a time.

Plan B, if you have purchased an inexpensive 5-gallon, plastic, clean-smelling, bucket from your hardware store, put some water from the tank in the bucket (when you aren't treating & seasoning water in there), move the Corys & feed them there. That is a little traumatic.

A fish bowl might work just as well. Maybe start them with a tiny bit of frozen food (defrosted in cool water, gently rinsed through a fine-meshed net to get any "organic soup" outta there) fed to the "spot". When they get accustomed to feeding there, buy a portion of California blackworms. Rinsed every second day, those worms, kept not too crowded in a flat container, will last months in a refrigerator. You might have to take a razor blade or X-acto knife & cut them to size.

Plan C for your extra shrimp is to sell some on-line with aquabid in a safe mailing time. One should ship in a Styrofoam container with a cardboard box fitted around it. Regular shipping tape should seal it all. Double bag your shrimp. Bag one should be a little loose to account for pressure changes. Tie it off & invert it in another bag. Tie it. Then tie a trash bag around them all. That matches up quite well with USPS shipping regulations for small cold-blooded invertebrates.

Those shipping boxes are the same that the blood drive people can use once. Check with them. veterinarians, pharmacies or the fish section of super markets for other styros.

Plan D might work if you deal with an independent pet shop. Some will give you a credit or straight out swap for merchandise. Value are modest. I drop off extra hornwort at a place & my black worm portions tend to get a little larger.

Plan E is Google your area and Aquarium Society or fish club. They often have spring & fall auctions. Meetings have mini-auctions where prices are modest, but a high percentage goes to the seller. (The goal of that latter is just to make the meeting more interesting.)

Plan F might work if your 10-gallon stand is an over/under stand. Move the cherry shrimp tank to the bottom. They tend to thrive in cooler "household" temperatures. Set up the little Corys with small tetras, Danios, livebearers or killifish in the top stand. Of course if you (also) suffer from MTS or Multiple Tank Syndrome, just move the Corys.

I have several empty planted tanks with too much algae. If you lived in the Chicago south side burgs, I'd arrange to buy some off you, rendezvousing at the location of your choice. ;)

Ok that last one isn't so viable. But if your pet shop has a bulletin board or the grocery or library has a similar board, post them for sale,

There are a lot of fish that will eat shrimp, but there may be an "invite a tiger in to eat the mice" factor. The use of a warmth loving German blue ram in with the cool loving shrimp was an interesting idea. I would look only for small predators (1-1.5") that didn't get very large. Even some small cichlids if not consistently well fed (Nannacara) might voraciously clean the shrimp out.

The dwarf African frogs, especially if they "nest" in floating plants well above the shrimp might work. Bettas, Bolivian rams (that can get a lot over 3" long) or a school of tetras may devour more than you want to lose. They may or may not also give the Corys (hastatus, habrosus or pygmaeus) more trouble than you want.

Good luck & all the best!

Malthus and Darwin pretty much proved that the balance you want to establish in a micro-ecosystem does not even exist in huge ecosystems but instead there is a cycle of boom and bust. If nature can't do this balance thing in an area of thousands of square miles, you are not going to do it in less than two cubic feet of water. If you want a balance, you have to do it yourself. With an artificial color form such as the cherry shrimp, you really have to keep your hand in the process, picking out the few reddest shrimp and removing all the rest.