I just got off the phone with Hydor and after having me test all my power heads in different buckets and in my tank for about an hour. At the end of the testing he asked me how much my voltage meter cost and apparently it didn't cost enough. I bought an analog meter and I wasn't accurate enough with my numbers and they didn't add up exactly. What did add up was that 4 power heads of different sizes all Koralias put out almost 100 volts. He wanted me to send them back so they could do some testing on them of their own. I would have to send them back with my own money and that's all would come of it. They are past their two year warranty. I asked what I would get out of the deal and he said they would look at them but could do nothing if they are past their warranty date. They tried to con me into sending back faulty equipment that i would not be compensated for. I am very upset with the run around i was put through. I was on the phone sweating and running around doing everything he asked for an hour. All so he could reiterate to me the knowledge I bestowed upon him at the start of our conversation, (that the power heads are past their warranty date.) I would only suggest buying Hydor koralia power heads if you want them to eventually leak a ton of wattage into your tank over time.