If you had multiple tanks available, you could do some nice comparisons.
Like one tank with pea gravel and tap water, one with enriched substrate and tap water, one with water column dosing, and one with both. Add CO2 or not.
If they are 10gal tanks, you can put them side-by-side under the same 4ft fixture to make that a constant.
Like one tank with pea gravel and tap water, one with enriched substrate and tap water, one with water column dosing, and one with both. Add CO2 or not.
If they are 10gal tanks, you can put them side-by-side under the same 4ft fixture to make that a constant.