The amount you'll need will vary, depending on your system and livestock load. The best way to do it is to test your levels and see what your results are. The maximum amount you can put in is generally governed by your evaporation rate. You can use it as top-off instead of RO/DI. However, you also have to drip it slowly, and dripping at night is better than dripping during the day. Another limiting factor is pH--it will raise your pH, so you'll have to monitor that as well.
You'll basically just need to get some test kits and check Ca and alk regularly to ensure that your dosing regimen is satisfying your sytsem's needs.
