The tank might be a little too small. My 46 gallon tank has a cleaner shrimp and a peppermint shrimp, and when the cleaner shrimp gets near the peppermint shrimp, the cleaner shrimp will scare it away or try to harm it.
The cleaner shrimp doesn't get hold of the peppermint because its too fast. I don't know how fast sexy shrimp are, but in a small tank, the cleaner might harrase them, as it does with my peppermint.
The cleaner also might not be able to harm them if the sexy shrimp have a host like an anemone or LPS coral.
I think that cleaner shrimp become more aggressive towards smaller shrimp when they are bigger. But the cleaner usually doesn't hurt the shrimp, unless it catches them.
but if sexy shrimp are fast, and they have a host to hide in, you shouldn't have to worry that much.
