I've had a pajama cardinalfish for 5 or so years now. I purchased him when he was a decent size, and at the moment he is living in a 75 gallon with two occellaris clownfish, a longspine urchin, some hermit crabs, and an engineer goby. A few days ago he started moving his fins more rapidly than usual. Yesterday he started perching like a hawkfish on the sand. I checked the water paramaters and the nitrates are a bit high (around 30-40 ppm), but he's survived multiple tank crashes in the past. Anyone have any idea why he might be acting in this manner?