I pulled out all but 3 lava rocks today, fairly small chunks, and added some sand. I haven't seen much of the shrimp in the tank lately due to the large amount of space they had to hide in, so it was nice to get a head count, of sorts, and confirm that the majority are indeed still alive. They can hide behind the sponge filter still if they really need a place to be completely hidden, as well as around the stones.
My amano zoeas are doing insanely well in that tank. It's frustrating because I've spent $50-100 setting up a system where they could develop and have access to phytoplankton and all the rest, but have only had 1 completely successful shrimp. In this tank I threw about 20 in and gave them no support whatsoever. I now have at least 4 that are nearly ready to transform into adults and another 6-10 that are promising. Unless there is a major dieoff, that's a 25-75% success rate versus a 0.25% success rate with the others. This tank will never be able to support hundreds of zoeas at a time, but I don't really want hundreds of amano shrimp, so that's just peachy.