Make sure your baffles are strong enough. I first started using thin plexi-glass... if there's a variance in water level in the sump, the weight will be on the baffles. For instance, I have my return chamber in the center. The drain is on the left and a fuge on the right. As evaporation occurs in the return chamber, the water level will slowly drop causing more weight on baffles that partition the return chamber. It started to bow a little bit. I took them out and used glass baffles instead. The glass was also thin, less than 1/4", but it doesn't flex like plexi/acrylic.