Yes I would cut the powerhead.
I had to look up 64 ounces
Using english measurements is no good for us english. lol We have been accustomed to metric since we were temporarily conquered by Europe. Hopefully that will be a thing of the past soon and we can return to Imperial everything like the rest of the 'real' world.
They even tried to ban beer being served a a pint!!!! Not a chance.
I would definately get some water movement at the surface. The reason most don't is because their CO2 level struggles however your venturi method seems to be working great. When I first started having a turbulent surface (flying in the face of convention as always
) I noticed my water clarity improved considerably.
Water clarity is a funny thing. you think it's like crystal until it gets clearer and then you think its crystal until its clearer again. lol Its always hard to convince people that they can further improve their water clarity.
I don't mean rapids or anything like that. I mean just so you get a good ripple:
Ignore the KH/Ph charts. They will not tell you with any accuracy your level of CO2. Your fish are telling you that your CO2 is high. Therefore if you lose the diffusion efficiency at night and then release a little more during the day you should have enough. When your DC arrives then you can gauge this better
So it looks like you venturi is super efficient and your mixes are working well. Keep us updated
AC