So I guess the new set up is casing a air bubble in the intake from the tank, so every so often the stand pipe gurgles. Is there any way to fix it?
See Hoffman grugle buster.
Cannot forget a name like that.
I'd likely suggest getting a wet/dry box, then sealing it with weather tape/duct tape 2-3 layers etc, this way when the water comes down, it hits that, degases in a sealed chamber.
So it's not escaping.
It redissolves back into solution.
Then there's no turbulence after that till the return pump in the sump = minimal degassing.
I use a slide out drip tray and reseal it if I need to change the filter pads, etc, but I rarely use the filter pad, the screen on the weir box/overflow catches most of the big stuff, then bacteria/shrimp/snails decompose the rest.
I have an Ocean clear post filter on a couple of tanks for polishing. You could add a UV somewhere also if you wanted.
The biomedias are generally the bio balls in the wet/dry section, then in the low flow sump: open cell sponge, 15 pores inch range then another 30 pores/inch. I clean those every other week depending on the tank's loading.
The sealed dry section prevents the loss I think is the key as the water comes down to the sump area.
I also suggest using hang on prefilters, they tend to be quieter, take up less in tank space, lose less gas. You can take them off and take a pic without anything in the way etc, or go back to canister etc if you want later.