I run a quanvee in-line diffuser on my 60u w/ a surface skimmer/ lily pipe.
I know bubble count isn’t exact but I was told my 5-6 bps is way too high for my tank. So that my dissolution percentage is bad. So the only thing I’m thinking is that my in-line diffuser sucks but other than that Idk what else can be the issue. Any insights ?
As you mentioned, BPS is not a good way to determine CO2 levels if you are trying to establish a given CO2 level. Once you know roughly where your CO2 level is, and have it set where you want it, then you can use BPS (if you can count them) as one of the checks to verify that things are running as you want. BPS will differ with every tank, not least of the reasons being that dissolution techniques range in their efficiency, as you are discovering.
An accurate CO2 reading requires testing equipment that costs more than most can justify spending, so we use several crude approaches to get us in the ballpark. Generally, once we are content with our levels, we will then push it higher - slowly - to the limits of our fishes ability to stand it and settle just below that limit.
As
@Phishless mentioned, a 1-point drop is one way to gauge this, but there are issues with measuring this way. Like all other techniques, it is just a ballpark estimate that will guide you to a level of ~30 ppm, particularly if your de-gassed pH is in the 7’s. In a similar vein, comparing pH of de-gassed water to fully-gassed water can also guide us. We also use the pH and KH readings to gauge CO2, either with calculators or charts. Drop checkers are also general guides to accomplish it.
All of these techniques have their flaws, not least of the reasons being that they depend upon hobby-grade equipment and conditions, e.g.; economy-grade pH pens and KH test kits or imprecise indicator solutions in the dc.
When attempting to establish a CO2 level, I use all three of these methods and look for corroboration among them. I then push a little higher and depend upon my fish to tell me when enough is enough.