I have a 20g reef setup I've had for a couple months now. I've been slowly adding soft corals and they have been doing well. I really like Hammers and frogspawn. It seems they need to have stable calcium. I don't care to add a dosing system or any other equipment to the 20g as it is beside my bed. So my question is do I need to supplement calcium if I do a 5 gallon waterchange per week? That may be a laughable question but I can't find much about this. TIA