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re: calcium requirments?

     ChazzHess at aol_com writes:
     >> I've noticed that I haven't seen any calcium listed in the PMDD 
     ingrediants. [sic] I know most (all) of the N and P requirements will 
     be met by my fish waste but I live in an area with very soft water.  
     Should I be adding a calcium source into my tank as well and if so, 
     how much should I add per gallon? <<
     If you have very soft water, you should add a calcium source. Calcium 
     carbonate can be used at 1 tsp for each ten gallons of water to give 2 
     degrees of general hardness and carbonate hardness. If you change 25% 
     of your water at least monthly, you will not suffer any calcium 
     shortage. So if you remove 10 gallons and add 10 gallons, you will mix 
     1 tsp of powdered calcium carbonate to a large jar of water, stir and 
     add this cloudy mixture near lights off time. Don't add calcium to 
     water added to make up evaporation losses.
     If you have organic soil in your substrate, it may be producing plenty 
     of nitrogen (nitrates) so that you will not require the nitrogen 
     sources in PMDD. I also use a reduced amount of trace elements from 
     the PMDD dosages since soil contains many of these nutrients and the 
     dosage in PMDD (aside from Fe) of trace elements is probably too high. 
     If you have a low fertility substrate, PMDD should supply all the 
     additional nutrient requirements except calcium. Fishfood will supply 
     the P requirements but alone probably won't supply enough N.
     Steve Pushak in Vancouver BC