usually monti caps turn brown over night from a phosphate spike. Just add a phosphate remover media. In my 14g biocube, i bought the filter chamber from intank that fits in the second compartment and ran chemipure elite, purigen, and filter floss on the top. I had little phosphates in the system since i used lr from my 125g and just bought new lr to replace the ones i took out from the 125g. They will get their color back. If you are going to dose, i would rather wait an hour vs a few minutes but a wc is even better for the size of your system. i never dosed in my 14g since when something was out of wack like cal or alk, i just did a wc and it brought the levels back to normal.