There is actually a slight defect with koralia evo. This came straight from their site:
Hydor has discovered a slight modification is necessary to ensure the proper functioning of some Koralia Evo Pumps.
The issue is that some pumps can run backwards over time when used with certain timers and wavemaker devices.
The problem can usually be corrected by a simple cleaning of the impeller bushing, bushing o-ring and bushing housing with any safe solvent such as rubbing alcohol.
Hydor will soon have a modified bushing and bushing housing available to the consumer at no charge.
Please contact Hydor USA at any time for assistance at 916-920-5222 or 866-493-6787 or
hydorusa.office@hydor.com