Back about 10yrs ago when I ran my turf scrubber, {oh ya we did that despite what, nevermind,
}. Anyways, I always scraped my 240sq. in. screen in the fishroom sink. But at times I did have some get in the aquarium for various reasons and, the odd time, I fed some of the algae to my tangs. That would be the good looking pieces and not the slimy stuff.
Although I had some alk. problems back then with my 225g, I never had a problem with fish loss. I dont recall any large difference in my tanks after scraping the screen. Sometime when I slacked in upkeep it had a ton of algae on it and I would remove it right to the screen without problems.
Others I imagine remove a lot of algae from their refugiums without problems to. Just a weird thing to figure out.