There is debate whether or not assassins will eat dwarf shrimp, with several threads started about it. People have different opinions. Its safe to say if the assasins have a proper source of protien, (bloodworms, pest snails) they should not harm a healthy shrimp.
I for the longest time, I agreed that they do Not eat dwarf shrimp. Until recently. I witness an adult assassin snail grab and eat a dwarf blue tiger shrimp. :( So i don't think it happens very often, but it can happen in my experience.
These little guys are are a great way to get rid of pest snails in your aquarium. I added about 40 assassin snails into my 68 gallon, and within a month, there isn't one pond snail to be seen (i had at least 400 pond snails in my tank before). They usually take a few weeks to really pick up the speed in eating other snails. Be careful when putting these snails into an aquarium with larger snails though (nerite, spixi, apple, etc). I noticed that they sometimes group up to take down a large snail, and they've been pretty successful.
Im new with these snails, but so far i really like them. I have a planted tank so pond snails and ramshorn snails are all over the tank. In a week or two they have eaten most of the snails. They are very hard workers.
I put 11 of these in a 6 gallon tank that was overrun with pond snails and also had a few trumpet and rams horn snails. It took about 3 weeks before I really noticed a change. They killed the trumpet and larger pond snails first. They killed a really big rams horn but never ate it, so after 3 days I took it out of the tank. They are laying eggs now in the roots of an anubias nana plant and the eggs are in rectangles of gel. All in all I am happy with them. They are keeping the snails in check in this tank.
Mine did not bury themselves and die. I moved them to a 40 gallon tank several months ago and they wiped out hundreds of MTS. They also reproduced quite a lot. I started taking down the 40 gallon tank a couple weeks ago and I have found about 50 assassin snails of all sizes in there.
I've had a two of these in an overrun 2gal nano tank. I can't say that they did too much for the nuisance snail population. I saw one of them literally slide right over some smaller snails on the glass. But, the adult population seems to be at a min, but I've also been removing the larger ones when I see them. It seems like they could care less about the red cherry shrimp and plants they're housed with.
I have a 10 gallon with 25 Assassin Snails 1 Amano Shrimp 2 Ghost Shrimp. I put Blood Worms in and watched a Assassin Snail crawl up to a Ghost Shrimp and steal his Blood Worm right from his mouth. They fought over it for awhile then the Assassin Snail won the tug of war. The Ghost Shrimp got angry and stood on top of the snails shell after loll
I had a 38 gallon with tons of Ramshorn, I added like 6 snails and the population dropped greatly, I love the sight of the dead snails in my tank. Otherwise I don't think getting a ton of them is necessary cause they will actually breed. They'll each lay an egg a week so getting tons just means eventual hidden pollution.
I bought two of these (must have been a female and a male) and after a few months my snail problem was under control. I've not seen them bother my shrimp nor eat each other now that I have a couple dozen of them. I have heard of feeding them piece of chicken or wafers with protein in it.
They will eat any food meant for inverts, including algae wafers, if nothing else is available. They do seem to overlook smaller snails, preferring larger snails. We put 1 assassin in our 6G Tall and within a month he cleaned up our pond snail problem... now we have to feed him!