Roger,
sorry to jump on an old thread, but I was wondering if it was possible to have two streams at opposite ends of the tank with one at 100%, the other at 30% and for them to switch after, say, 6 hours. This would prevent the problemn with animals or propellers getting killed. I can't work out how it would be possible, but surely it would be a very desirable option to have?
Thanks,
Matthew.