I'm already dosing both epsom salts and baking soda to increase the KH and GH (KH around 100 and GH around 60), but this still leaves out the calcium component. The substrate is rocks but with about 1/2 inch of natural sand underneath which raised my KH straight off from 60 to 100 so I'm assuming that the crushed shells in the sand might be releasing calcium carbonate. I am also dosing KNO3, KH2PO4, K2SO4, and Plantex CSM+B. (plus aquarium salt 1tbsp/5 gals just for fish) My water changes involve many bottles and powders and measuring spoons all over the table as you can imagine. I'm still trying to get my co2 stabilized but it's at about 25ppm right now. I have only two 20watt lights. What else do I need to dose? The tank has had plants for a month but fish for only 6 days. The plants are pearling now that I have co2 going. I also had brown algae at first till I got my pleco who is keeping it nice and clean now. Maybe I should get GH booster instead of epsom salts. But if I were to let my KH get back to 0, with the co2 added we're talking super acidic water.
(without co2: pH is 8.2 with added baking soda, 6.6 without. With co2 pH is 6.8, that's with the baking soda)
Well, I suppose if you enjoy all the spoons and bottles then that's one thing, but from my perspective it would become tedious after a while so I would try to consolidate as much as I could.
As we've discussed before, if you use the GH booster you could immediately eliminate a) Epsom Salt, b) K2SO4 and c) calcium chloride.
I guess I don't know what "aquarium salt" is (is the chemical composition listed on the package?) and I can't imagine what freshwater fish would actually require it in an aquarium but I would be willing to bet that it's probably got Mg, K, maybe Ca, maybe Chlorides and Sulfates. It undoubtedly cost more than GH booster. The plants are certainly using it but these would all be duplicated with the GH booster. So I think you can probably eliminate "aquarium salt" as well.
If you say that the kH rises due to the substrate then there is really no need to add Bicarbonate, and as Hoppy points out, it's no big deal if the kH is low. So the pH drops, so what? The fish will get over it, I mean, especially if they are Central/South American species where the waters are acidic, right? So I'd vote for eliminating Bicarbonate as well.
So to summarize, adding the GH booster and leaving the substrate to buffer the kH by itself allows you to to forget about 5 different products. Obviously NO3, PO4 and CSM+B stay. That should make water changes less complicated by an order of magnitude I would've thought.
One more thought; When you measure the tap water pH are you measuring it immediately as you draw it from the tap? Tap typically has some dissolved CO2 which would drive the reading low. What is the tap pH after you let it sit for an hour?