My tank is 3.2m wide. I got 3 * MP40 at each endpoint. Yet over time I found that they do not provide enough flow, especially in the middle part of the tank. had 2 BIG Voyager 16000L/h in the middle but they packed up due to old age beginning of the year. Thought that all those MP40 would be enough, but during the year I got algae growth on the rocks. And it is due to settlement on the rocks. Had to take out parts of the system and scrubbed the rocks down plus rinsed them out a lot.
The tank is very close to the wall. 1cm gap between the back of the tank and wall. With a piece of ABS sheeting covering that gap. NOTHING, as in no livestock has gone over the back of the tank. They simply cannot, not even snails. The downside is that I cannot get any pumps on the back pane that got big magnets.
Got myself the best bang for buck pumps that's available, SunSun 10000 L/h with magnet mounds JVP133. Their magnets are luckily thin enough to slide down the back using braai tongs. They are big, bulky and BLUE! But for under R500 per pump, they got the best Rand to flow ratio of any pumps out there. And I can already see the difference after just over a month. Plus they are not that blue anymore.