PH flow between K8 and a MP60

[jmccown]

I have a 500g 7x3x3 tank currently using a K8 for flow. It is a FO tank. The acrylic is 1" thick so the K8 magnet is not strong enough. In reading the Vortech MP60 is for up to 1" thick but is $750 bucks, quite a jump from the price tag of the K8. If I could get the K8's to hold better I'd just pick up a couple more of them and be happy. Is there anything stronger but not as pricy as the MP60's? Say less than $300? I don't want to do closed loop.