Some years ago, some very effective bromine salesmen, presumably from Great Lakes Bio (bromine company of the era) were able to pull the wool over the eyes of a number of code authorities and pool stores in New England. The effects of their sales efforts are still being seen, lingering in some New York codes and in cases like yours.

Compared to chlorine, bromine is overpriced and under-performing even for indoor pools. For outdoor pools, where it cannot be stabilized against photolysis by solar UV, it's MASSIVELY more expensive. I'd recommending switching to chlorine.

If you don't want to do so, that's fine, but we don't support bromine use. I'm one of the few here who knows anything about it, and trying to support it becomes a distraction.

Unfortunately, in cases like yours, switching requires a total drain and refill -- INCLUDING a washdown, partial refill, and flush of pipes and filter. The problem is, if even a little bromide (used bromine) + hydantoin (the chemical 'binder' in solid forms of bromine) linger, you will continue to have a 'bromine' pool, even if you USE chlorine!

The reason is, chlorine is a stronger oxidizer than bromine, and oxidizes bromides (used bromine) BACK to active bromine -- but the chlorine is destroyed (reduced to chloride) in the process.

A couple of other issues:

1. You don't need a bromine kit: the ONLY difference between a chlorine kit and a bromine kit is the numbers: for a given color, the bromine numbers will be twice (2.25, to be exact) the chlorine numbers.

2. Oxygen shock (non-chlorine shock, potassium monopersulfate) is an EXPENSIVE, inefficient way to oxidize bromides back to bromine. Just using chlorine, including 8% plain household bleach is a much cheaper, more efficient way to accomplish the same thing.

Recommendation #1: Drain, rinse, refill and begin using chlorine. (Pressure wash any algae, but be careful not to strip paint or weak plaster.)
BE CAREFUL: if the pool is not elevated significantly above the ground water (swamp?) I saw on Google Maps, just north of the house, when processing your registration, DO NOT DRAIN THE POOL. Even concrete pools can float out of very wet ground.

Recommendation #2: If you want to think about it for awhile, just use bleach, dichlor or whatever form of chlorine is most cheaply available to you to raise bromine levels high enough to eradicate the algae. (ANY form of chlorine will simply react with the bromide reservoir to form fresh bromine). Add chlorine LATE in the day, so the bromine formed can 'work' all night, before being destroyed by sunlight the next day.

If the pool has been operated a number of years using solid bromine, but without being drained and refilled, it may take VERY large doses of chlorine to form high enough levels of bromine to be effective. A large hydantoin residual greatly weakens the effects of the bromine present.

Let us know if you decide to convert to chlorine, so we can guide you.