Thank you for your answer
I've been using some crushed coral on the bottom of the small snail tank to keep the pH above 7 (since it doesn't dissolve much in pH over 7, I think it will start dissolving more if the pH crashes under 7, and so works as a sort of buffer) and added baking soda and gypsum, CaSO4. I just don't like the gypsum because of the sulfate it contains. I will be using potassium sulfate and maybe a bit magnesium sulfate (or do you think I don't need to add any Mg?) in the planted tank, so if I would add calsium sulfate too, there might be too much sulfates in the water.
Is there any (not too expensive) pure calcium source?
I think I should calculate a good recipe for my PMDD, I've been using the regular one mostly used here in Finland, but since I know what's in my water I could try to get the recipe as useful as possible. I use potassium and magnesium sulfate, chelated manganese and iron and Hortigrow Mikro containing: B 0.33 g/100 ml, Cu 0.05 g/100 ml, Fe 2.0 g/100 ml, Mn 1.14 g/100 ml, Mo 0.025 g/100 ml, Zn 0.3 g/100 ml. I also have potassium nitrate to add nitrates to the tank. And I do 50% water changes every week. I won't be using PMDD every week, but every three weeks. 1. week: PMDD, 2. week: Tropica Master Grow, 3. week: Seachem Flourish and Flourish Trace. I am thinking about doing this because I'd like to give the plants best care possible, and since all the fertilisers are a bit different, varying the type will give best results, right?
I will be doing some reading and update my knowledge about PMDD and check how you all dose it. But if someone has spare time, I would really appreciate help with that too