Sure seems like a good setup. A few things that I would just check:
- Verify your water temp with a different thermometer or whatever you are using to measure it now. About 78 or so is on the upper end of what most people recommend. Given that you have the top on the tank, and if you are going by what your heater is set at (they are notoriously bad at heating to what they are set at) you might be warmer than you think.
- Is there anyway they are getting sucked in or pushed around by that powerhead that is powering your sponge filter?
- Maybe get a cheap 10 gallon tank and use one of your sponge filters and move your Amanos to it for a week or two - just to rule out if they are bothering the RCS? I had a few Amano shrimp for a while with my CRS, and they didn't seem to bother, but I found the CRS much more interesting anyway, so I took the Amanos back for store credit.
- Are you dosing anything for your plants?
- Any other possible predators in your tank? I once had a dragonfly nymph that I saw one day, and had no idea what it was. It scuttled away and I thought it seemed weird, but at the time didn't know how dangerous they were. A day later I saw it again, and it then attacked and killed one of my CRS shrimp. Luckily it was by the front glass, and I took a net and caught it. Thankfully, that was the only one that hitchhiked on some plants. However, on a big tank with lots of hiding areas, something like that could be hard to see.
Just throwing out possible ideas, from what you describe here, nothing immediately jumps out at me as to what might be wrong.
- Verify your water temp with a different thermometer or whatever you are using to measure it now. About 78 or so is on the upper end of what most people recommend. Given that you have the top on the tank, and if you are going by what your heater is set at (they are notoriously bad at heating to what they are set at) you might be warmer than you think.
- Is there anyway they are getting sucked in or pushed around by that powerhead that is powering your sponge filter?
- Maybe get a cheap 10 gallon tank and use one of your sponge filters and move your Amanos to it for a week or two - just to rule out if they are bothering the RCS? I had a few Amano shrimp for a while with my CRS, and they didn't seem to bother, but I found the CRS much more interesting anyway, so I took the Amanos back for store credit.
- Are you dosing anything for your plants?
- Any other possible predators in your tank? I once had a dragonfly nymph that I saw one day, and had no idea what it was. It scuttled away and I thought it seemed weird, but at the time didn't know how dangerous they were. A day later I saw it again, and it then attacked and killed one of my CRS shrimp. Luckily it was by the front glass, and I took a net and caught it. Thankfully, that was the only one that hitchhiked on some plants. However, on a big tank with lots of hiding areas, something like that could be hard to see.
Just throwing out possible ideas, from what you describe here, nothing immediately jumps out at me as to what might be wrong.