Sorry I may have said what I wanted to say wrong....
Silicates are a mineral. If your tank has a detectable amount you can see brown(diatom) algae growth... It mostly comes from your glass or water source(whatever you are using to change the water or top off with)... Brown algae is usually the first wave of algae and expected during a cycle... It is not neccesary for you to test, but you had asked earlier what kits you may need, this is something you may want to consider(especially since the kits are realtively cheap compared to the others, wanna say like $10 for 50 tests). If you decide to test this, also test your watersource.
If the brown algae does not turn into green algae around weeks 7-10 you could have a build up of silicates... But from the pic it looks normal and fine for your progression.
Sorry for the confusion