re: rockwool

---------- Forwarded message ----------
From: "shaji (s.) bhaskar" <bhaskar at nortel_ca>
Sender: "shaji (s.) bhaskar" <bhaskar at nortel_ca>
To: aquatic-plants at actwin_com
Subject:  Rock Wool - Good or Bad? 

The major concern here seens to be that the rock wool is saturated
with nutrients which can cause an algal bloom.  

An analysis of a hydroponic nurient mix from Technaflora (which, I
assume if fairly typical of commercial products) shows that adding a
few plants to an aquarium without removing the rock wool will not
introduce significant amounts of nutrients into the aquarium.

Technaflora (see http://www.getset.com/technaflora) lists its mix
as having the following composition when used as recommended:

Nitrogen (elemental/NO3?)    200    Phosphorous  (P2O5)          90
Potassium  (K2O)             300    Calcium                     200
Magnesium                     30    Sulfur                       50
Iron                         1.6    Manganese                    .4
Zinc                          .4    Boron                        .3
Copper                        .1    Molydbenum                  .05

Let's say that the rock wool contains about 20 cc of this nutrient
mix.  This introduces about 90 mg/l X .02l = 1.8 mg of phosphates
into the tank.  If the tank is 100 liters (about 25 to 30 gallons),
the phosphate concentration will go up by 1.8mg/100l or 0.018mg/l.

An increase of this magnitude does not seem worth bothering about.  If
you are introducing 50 pots, all at the same time, into a 25 gallon
tank, you have cause for concern.