I had rosy barbs following me when I scraped the glass with the razor blade. Never hurt one and they were frantically trying to get the scrapings. A credit card works almost as well as those spots are very hard and can almost pop right off. Seriously disliked the algae pads as it was very difficult to get GSA off with them but it sure is safer than a razor blade!
Had GSA until I started dosing more phosphate in my bright, CO2 enriched and fertilized tank. All gone now. Good thing as Anubias collects it like mad and of course algae pads, Mr. Clean sponges and the rest wouldn't work on live plant leaves!
How much light is over the tank? 7 hours is a fine photoperiod but perhaps there are too many bulbs over the tank. Could raise the lights, shade them or turn off a bulb?