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

Thanks for that bloodasp.

So far so good with mine.

I did notice one thing however. I mentioned earlier that they were completely silent. this is not true. My reeflo pump was shut down for 2 days and as a result, I could hear a lot of other things going on in the tank. One of them was a soft click you would hear every minute or so when the pumps turned on and off. this was likely happening on the first day i got them but just was not noticable due to the pump noise.

Having said that, the noise is not loud or annoying and the pumps continue to work fine.

Still recommending them!

We have sold several of the controllable koralias, and all of our customers have had nothing but good comments about them.

I have the GHL Hydor controller, with 2 x K4 controllables, running off my Profilux, and 3 x Evo 1400's. I am very impressed myself with all of the recent powerheads from Hydor.

Update on the evos:

One of them stopped working and another one clicks. The two other ones are working fine.

I tried my kora's on a cheap wavemaker timer, worked for about a day, then they wouldn't start. I noticed the reverse start sometimes too. I'm interested to see how this goes.

I picked up two of the new 4's for my frag system a few months ago. I did some reading on RC and the general concensus is that they should not be used on timers so I've just left mine running constantly.