Dolomite in substrate

[Anubias]

I am curious to know if anyone has added dolomite to their gravel substrate, and whether they have noticed any effects on plant, mainly crypt growth. In order to boost calcium levels I have done so, and added 2 or 3 tbsp at each water change over the years. Very little dissolves. I am speculating that the calcium combines with the phosphate making it sparsely available to the plant roots, thus limiting growth. Ideas?

[Plants245]

Hmm - gets me thinking. First, when you say dolomite, do you mean dolomite lime i.e. (CaMg(CO3)2)?

Assuming that you do, here is my 2 cents:

If the intention is just to boost calcium levels, then why not add CaCO3 --> I had read (and I have no links) that the ideal Ca:Mg ratio will be 3:1 or 4:1 and some people go as far as 2:1 ... if it gets to close (I read somewhere again with no link) to 1:1, then the Mg levels can mess with the calcium uptake of plants ... causing other deficiencies. But many plants don't take up THAT much calcium so much so that dosing it is needed (aside from remineralizing water with a water change) ... what you might be observing that limits growth is this.

The ions (calcium and magnesium) will just form an ionic "soup" in solution bouncing around with several variables, so I don't think it will selectively mess with the uptake of phosphate (do you notice phosphate deficiencies .. .and what is your phosphate level?)


In terms of Crypt growth, I have miracle gro in the bottom of my flourite substrate; they grow pretty well, I think. This is likely attributed though to those NPK pack-a-punch as opposed to dissolved salts.

Just another thought: With the consistent addition of dolomite, you will be pumping your carbonate hardness (with the addition of CO3), and, naturally, your pH ... which will inhibit the CO2 concentration -- maybe stunting growth?

[Anubias]

I broke down the tank, sieved out most of the dolomite. and replanted. Can't tell yet if growth will improve, but I also added some Osmocote slow release pellets under several crypts. This seems to work well. Calcium can be added to the water column via calcium nitrate if necessary. I have not tested phosphate levels in the water column. My guess is that many rooted plants will only absorb phosphate from the substrate, and that the dolomite might be binding with the phosphate. Oher nutrients seem to have been present in adequate amounts.