Iv had an rbta in my tanks for about a year. It has split 5 times and even servived the power outage las summer. Over the last 4 or 5 weeks i have noticed that they are all slowly shrinking!!! I cant find a change in my water but i did change the water flow. The flow over the rbta is much stronger and steady. Could this be causing the shrinkage or is there a water problem im not finding?? Thanks...