We just incorporated our two 29g tanks into one 75g. This meant our shrimp now live with a big plakat betta that thinks they look tasty. I put some moss in the cave and threaded it through a few holes to encourage growth outside. The shrimp are already hanging around it and the holes are small enough to keep the betta out.
I'm currently using these to hold large chunks of Java moss in place. Stuffed them full, and pulled bunches out through the holes. No more moss getting caught in my power head. Care should definitely be taken in regards to fish size. These are made of a pretty stout material, and cutting or breaking it to free a stuck fish, without causing injury, would be difficult. But, for what it is, a great product that I will be using more of in the future.
I use it to weigh down the blocks of frozen blood worm and to slow down the corys chowing down on it. Sorta like one of those dog toys one uses to stuff dog treats in. Helps keep the food localized to a feeding area so that detritus does not go everywhere.
Also trying to use it to weigh down riccia that I've cultivated. Hoping that riccia will grow out of holes and form a round bush.
This shrimp house is just the right size it's not so big that it takes up a lot space. I supper glued Java Moss on mine and it looks great. I'll probably be getting another one.