Jebao pp20 is a monster for $80. I have a 120 rimless tank with plants and floating water lettuce. I decided that I need a bit more flow, but it's hard to find magnets that work ok on 3/4" glass. I saw the PP20 and figured that if I got the big pump the mag would be strong and the product page says it has an extreme magnet.
Well the magnet holds just fine on 3/4", so that is right!
Problem is that this pump is a beast. Absolutly, easily, the strongest pump I have ever even seen. On the min setting in my 120 all my floating plants were compressed on top of each other, the drift wood went flying and even rocks (on BB) were moved.
I ran it 2 min and decided I had to sell it. But for a big tank it would be awesome. They have an adjustable power supply to dial it down even more, but in 4ft even that would be a lot.