for one dont go with eco complete. Its not all that much better honestly then sand. Amazonia or other ADA soils are amazing compared to. deff worth the cost. And again. you dont NEED 3" of substrate unless you have very large plants unless you like the deep substrate look.
Just realized it was a 90 gal which is the same as my 75 pretty much.I got 5 bags of amazonia thinking i would need them all but i ended up using 3.5 9L bags.
you said earlier you used 1/3 inch of power sand for your 75....how many bags of PS was that? I can only order the large size in 2L bags....dont want to overbuy it as its like $35/bag