So i have a 29 gallon lightly planted tank. Water paramaters are not an issue. Ph is 7.2. Tank had 5 juvenile hrp's and 6 juvenile apisto's. Everyone was fine for about a month and a half then one of the smaller HRP's died mysteriously. I just credited it to being a runt cause he didnt grow as much as the rest. Since then 2 more have died. I noticed that they constantly look like they are chewing. The only thing i can think of is oxygen, but they show no signs of oxygen deprevation and I run a aquaclear HOB and alwasy leave the water level a little low that creates quite a bit of surface aggitation. Also have a powerhead that circulates and makes alot of surface aggitation. All apistos are striving and look great. ANy ideas whats going on with them?