Hi, and welcome to the group!!

Before we can tell you what you need to add to the water, we need to know a starting point. You need a full set of tests, taken with a drop-based kit. No strips, computer readouts, etc. The kit we recommend is the K-2006 that can be bought online several places, but the cheapest we've found so far is through the Amazon link in my sig. Once we know where you're starting, we can help you get where you need to be.

The Floatron, which you describe as a pretty $200 floating device, is also one that is releasing copper into your water, which is not really a good thing. Copper does have algaecidal properties, but it also is what turns blonde hair, fingernails, and pool liners green when it gets to a certain point. That being said, I would strongly advise you to take a sample of your pool water to a dealer that will test for metals, and have it tested specifically for copper. The "metal agent" that's in your startup kit is probably a sequestrant, which is designed to keep the copper suspended in the water so that it does not precipitate out and stain your liner green. However, that's something that can be addressed later on. If it were my pool, I would take the Floatron out of the pool and repurpose it to a pretty $200 lawn decoration.

What is in the chlorine granules that your mother-in-law bought? (Need ingredients--cal-hypo or sodium dichloro......) What size pump and what type and size filter do you have?

I would go to WalMart and get several gallons of plain, unscented bleach, and if they have thehhth 6-way drop kit, get that too.....run a set of tests, post them here, and we can help you go from there. Alternatively, take a sample of pool water to a store that does drop-based testing (you're gonna need to do this to test for copper, anyway) and get a printout of those results, but don't buy any of the stuff they're going to try to sell you, no matter how insistent they are.

I would not shock the pool just yet. I agree that shocking is in order to kill off your algae, but shocking with high levels of copper in the water is going to stain your pool...that's why we need tests results to formulate a game plan.