Interesting. I originally had 2x Tunze stream 6000 ( 14,000 litres per hour total ) on my tank but upgraded one to a 6100 to give me 19,000 lph because the gigantea was gaping, contracting and expanding, etc. Within an hour of adding the extra flow it perked up and has been behaving normally since. That's a fair amount of light - 650 Watts - on a 75g. :eek1: