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Rondomatic Doser

I've just installed a new piece of equipment that I think will be a real
asset to tank management. It's the Rondomatic (love that name) Feeder by
Grasslin. This is the round one that has 28 little cups that dump out at
pre-programmed times. I was surprised by how big it is, it's 6.5 inches in
diameter. It's very nicely made, which explains the priciness - $63 at

I used Chuck Gadd's dosage calculator at
http://www.csd.net/~cgadd/aqua/art_plant_dosage_calc.htm and entered "1" as
the number of milliliters of water to mix with the dry fertilizer
components. Although this isn't really enough water to dissolve the dry
fertilizer, it doesn't matter because I am dosing it dry anyway, the
calculator is just a mathematical model of a hypothetical solution. You can
experiment with the weight/volume of a given compound in the calculator to
get the desired ppm of a given element. I worked out my weekly dosage of
each compound, divided into seven parts, and put the fraction of a teaspoon
in each of the doser cups. A month's worth of dosing accomplished in a few
minutes. No more mixing solutions, droppers, syringes or what have you. I am
using it to dose KNO3, K2SO4 and the CSM micronutrient mix, all in powder or
granule form. The fertilizers are dumped into the sump once a day where they
slowly dissolve and are dispersed into the tank.

Works for me.

Tom Wood