I wanted to update this, a lot has happened since I started out with 3 red claws in a guacamole bowl.
I ended up with a 20 gallon tank, centered around the crabs' needs, with the main focal point being a large driftwood flume that uses return water to create a shallow rapids area. The crabs both spend most of their time on this piece of wood, and half, if not more time above water. They both really seem to enjoy the running water, spending lots of time in it, and showering in the return, cleaning their eyes, eating bugs and algae. They also love to sit on and eat the terrrestrial moss that is growing on the wood. they don't seem to bother much of the other plant growth, but occasionally clip some brown parts off for me. They also love the dry and blood worms, and will eat them off my finger.
The crabs are known for being territorial and eating fish and inverts, so I wanted to make sure they had what they needed, and to introduce fish that could handle them. The terrain was important, and I see now that it really keeps them occupied. They have ample places to hide and hunt, without needing to go after the fish.
I started with 7 cherry barbs. Within minutes of introducing them to the tank, the crabs were in hot pursuit. their antics were really funny, but the crabs soon realized the barbs were too quick... and the barbs seemed to mock the crabs. To this day, I haven't seen a crab swipe at a barb, even when the barbs enter the crab's cave or linger within an inch in the rapids.
Shortly after, I had an algae explosion. 3 Otos into the mix. the crabs were interested, but didn't even bother to get close. They knew there was no chance, the otos were quick as well.
the otos do seem to keep together and avoid the crab territories, which shows by the algae growth in them, but I don't think they seem too threatened, just aware and cautious. they are active and do venture around the tank... but they have an established territory they like a lot.
I needed to get rid of the algae, and didn't think another oto would do it. I introduced 6 amano shrimp to test the crabs's interest and hopefully dent the algae problem. The crabs didn't seem to notice, and I've seen up to 3 shrimp at a time in the crab's cave cleaning it while he was out. They seem to have no fear, and the crabs have been acting no differently.
I've made a few mistakes for sure, areas of my substrate are too deep, I started with a lot of stone, I created a lot of shade that won't support my plants... and I wish I could have given the crabs a brackish environment, but there were simply not enough viable options for fish, especially algae eaters, that would work in the small environment if brackish. It didn't seem feasable as a first aquarium for me. Only time will tell, but they seem good, and have both survived a moult.
Anyway, I hope this is insightful for people looking to introduce red claws into a community tank. They are really entertaining, and very smart and alert, I really enjoy mine.
