So, I got my 4 new Brigs last week and they were healthy, happy, beautiful, zooming all over the tank. Yesterday I noticed they hadn't moved much, so I just kept an eye on them (and 1 I can't locate). Today I did the sniff test on the 3 I can find - no one stunk, so I set them back in and put food next to them. 2 of the 3 had a little snack and then they wet to the back of the tank and partially buried themselves in the sand. The 3rd still hasn't moved, and the 4th is nowhere to be found (didn't come out when I put food out). It's a 20 gal and the params are 0 ammonia, 0 nitrite, 10 nitrate, pH 8, and temp 79.5 F. Last water change Sunday - 50% - treated with Jungle Start Right for chlorine and metals. Tank mates - ~15 blue pearl shrimp, several ramshorns, and ~ 30 (most teeny tiny - 1-2 mm) MTS snails. There i are also quite a few live plants. Ideas???