Two reasons to use close loop:
1. You hate the look of power heads inside your tank.
2. You just woke up from a 10 years coma and not realizing the advancement of wave makers these days.
There is a third reason, almost left it out: you are so old school keep living in the past.
Just kidding, close loop works, just no longer popular these days as many wave makers are powerful and inexpensive.
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