I finally caved in and bought a phosphate test and checked my water.
Tap .75 ppm
55 gallon tank somewhere between 2ppm and 5 ppm closer to 5ppm though as it had more of a blue tint.
75 gallon same as the 55 but a bit less blue.
Now the 55 is planted but mostly slow growing plants like anabuis and crypts. The 75 is heavily planted with fast growing stems and a few slow growers.
I did dose phosphates last week, 55 gallon got 1 ml and the 75 got 2 ml of fleet. I have since done a 50% water change and not added back.
I don't have a GSA problem in the 55 gallon but I do in the 75 gallon, thus the reason I bought the test.
Why would a tank with so much phosphate still have GSA?
Granted its not bad, just on the anabuis and the sides of the tank I can't reach to scrape. Also on one cave decoration but I like it there as it looks more natural.
1.75 wpg on both tanks, Excel in both tanks and EI dosing.