some live microbes(ie. dragonfly earth meds, ogbiowar, tribus) but letting your pots have good dry downs is the best thing you can do for your roots. if they aren't searching for water growth becomes stagnant.
Silica
148g (Potassium Silicate) to liter water makes a 7.8% concentration.
2.5mL of concentration per gallon gives a Si ppm of 23ppm. (and 24.5ppm of K)(~48ppm SiO2)