I see no power heads for flow. Sounds like oxygen depletion if the clowns are at the surface
On your guys' note about lack of flow, when you say "flow" does the flow need to be coming from the bottom towards the top of the tank? Like a power head near the bottom pointed upwards? Or do you just literally mean water moving throughout the tank. I ask this because I am currently running the Sicce Syncra 1.0 that moves 251 gph. When I first put the nem in the tank he moved around for hours all over the tank and finally settled on a spot in the back behind some rocks where the flow was much lower, sometimes I will turn the pump off for a few mins to feed and he will stretch his tentacles further to where when the pump comes back on I can see the flow is too much and it waves the long stretched tentacles everywhere and he will shrink back up a bit. So moving forward I'll have the addition of a UV sterilizer and a skimmer, what else do you suggest/ thoughts about power head placements.The bacteria is causing the lack of oxygen. You need to get rid of the bacteria bloom. Lack of flow in the tank will cause a lack of oxygen and possible die off that is feeding the bacteria. Get flow in the tank ASAP.
Thanks for the help