I placed the entire kilo block in the sump intake where there is indirect moderate flow. Total water volume on this system is 380g. Kilo block was about $25.

It's supposed to dissolve to replenish depleted elements:

SeaLab Concentrations (ppm)
Aluminum 0.01
Boron 4.6
Calcium 400.0
Chromium 0.00005
Cobalt 0.0005
Copper 0.003
Fluorine 0.3
Iodine 0.06
Iron 0.01
Manganese 0.002
Molybdenum 0.01
Nickel 0.002
Selenium 0.004
Strontium 8.0
Tin 0.002
Vanadium 0.002
Zinc 0.014

Claims...you can't overdose. Old school product that I'm hoping will just keep calcium up.