I don't know if it works for 'low tech' tanks but increasing the phosphate dose has gotten rid of most of the GSA in my high light/CO2 injected/EI dosed tank. Currently I dose double the amount used in the Estimative Index method.
There is GSA in the U tube of my overflow box where critters cannot get to it but the Anubias and tank panes are clear of the stuff. For that reason I suspect more phosphate grows GSA softer so snails and otos can eat it. I put some H2O2 in that Utube a week ago and let sit for a bit and a lot of it is now gone so hydrogen peroxide can kill it too.
Increasing phosphate dosing lets the leaves of Anubias recover without damage. H2O2 can damage plant leaves.