"Dave M. Picklyk" empowered us with this mighty blow
against the Patriarchy:

The problem is that when I turn my aquaclear filter down in the
morning when I feed, it stops bubbling and water siphons back into
the hose a few inches, then it has to clear it out again.

Err, that ain't good. It sounds like your Aquaclear is somehow
actually drawing CO2 through the line hose it's on ... if so, your
CO2 mix bottle might collapse. The CO2 should be coming from the
hose on its own (positive pressure).
I posted a message up here asking if putting the hose into the end of
the intake tube of the AquaClear was ok...thinking that the bubbles
will be sucked in and churned by the impeller, breaking them up and
storing them there for a while to absorb more C02 into the water
instead of it escaping...everyone thought it was a good idea and I saw
other ppl doing it too. How would you do it?

Well, I have injected CO2 directly into filter intakes before. For a while
I was injecting into an Eheim canister filter; I had the tubing cut at an
angle and loosely strapped to the outside of the intake strainer. I was
also injecting into a Fluval canister filter, for a while with the same
method, and for a while I had the tubing actually inserted into a hole in
the intake strainer.

I'm not really familiar with the design of the AquaClear intake; it would
seem to me that you'd need to restrict the flow of water through the
strainer in order to cause enough suction to actually pull CO2 through the
tubing. Or maybe it's due to the high flowrate of the filter? I don't
know.

Right now I'm running my CO2 into a Hagen Natural CO2 system diffuser, and
I'm happy with it. I'm getting good levels of CO2, the diffuser is easy to
hide behind some plants, and I don't need to worry about locking up the
impeller of my canister filter.