Oops, forgot to add - another issue with stuff growing in the reservoir is that the gunk could in theory at least foul the autopot valve so the float valve controlling nute intake does not seal completely. Keep an eye on water levels in your trays so you have a sense of how high the liquid in them gets. You will notice that the water level at maximum just barely covers the hose input fitting on the valve. If you detect it getting higher over time, or if it ever gets high enough to spill out of the hose groove, clean the valve immediately. If the float valve controlling the nute input fails to seal, the reservoir will empty into your grow space. Be a bit of a mess if it made it to a wall to wall carpet.