Brown Algea???

Yes!
There are a few things you could use. Saltwater algae control.

Chemi-Clean - Oxidizes organic sludge and sediment and clarifies water. Safe for reefs, invertebrates, macro algae, nitrifying bacteria and fish.

Red Slime Remover - Won't harm fish, invertebrates, corals, or reef inhabitants.

No-Cya-No - Works safely and effectively to interrupt the reproductive cycle of red slime. Safe for fish and invertebrates.

I haven't used any chemicals on my tank in 18 months. I use a brush to scrape brown algae off the back of my tank every couple of weeks or so. I let it grow on the plastic overflow boxes.

Ron, on a side note. You know that you're going to need about a 30g in about a year for your GSP. They get rather large, too large for a 15g. You've got the right idea so far though, unless the brown algae gets out of hand it's not really an issue. Just wipe it from the glass. Algae always means one thing, over abundance of nutrients in the water. Which is never a good thing when you're keeping puffers. Test your water for ammonia and nitrites, as well as nitrates (which is toxic to fish over 30ppm). Ammonia and nitrite are toxic period. You should also get more filtration as you should always have over filtration when keeping puffers.