Welcome to our forum.
First....to change, you have to change out the water.Jason,Store manager for a D-1 & Caldera Dealer
I'm using granular bromine, and if I know I won't be in the tub for a few days, I throw the floater in. I don't know what MPS is. I'm using a non-chlorine shock. I seem to have to use a ton of Bromine granular to get the same result I use to get out of a tablespoon of chlorine. I typically have to use upwards of 75 grams of Bromine granular just to keep it at 1-3 PPM w/ Ozone. Also, from the budgetary perspective, Bromine seems to be at least double the price of Chlorine.
Dont waste your time with the algacide unless you leave the cover off more than not or you alwas have the light on.Algae, like any plant (and no, not like the white algae, which is actually a mold), needs light to grow. Green may the result of copper, other metals, but most likely this is a reaction between the ozone gas and unsanitized water.
I'm fairly new to using bromine - but have been happily using it for the last 4 months. If water is properly kept it should not turn green in one day without tubbing.I have no experience with granual as I use tabs. I use nothing but bromine and MPS (non-chlorine shock) when necessary - I "go through" 5 one inch tabs about every 3 weeks or so keeping the Bromine level around 1 PPM. As a result my water has been fantastic and my bromine cost has been around $3 per month.