I dose my seachem very liberally. And don't bother with measuring to instructions. The savings come from time and not needing special water.
Sometimes I accidentally stir up sediments and cloud the tank, also add prime to detox just in case.
I have been using tap water for my top ups since I started with my first tank in 2007.
Currently, I treat it with Seachem Prime before adding to sump.
However, please do so with caution.
Our systems are very different.
If they look like sponge i.e. not solid but holey, then they are sponges. Some bros keep, some throw. If not, I cannot tell what is white stuff. But live algae is never white.
At the end of your cycle, you should have clear water, no foul smell and if you have lights on, algae (cyano also count) starting to grow. that is a sign of nitrate.