I have a floating raft system with hydroton in net pots. Since I started the system about five weeks ago, I have had mold developing (at least I'm pretty sure it's mold) on the top layer of hydration in the net pots.
I went to a local hydroponic store and they thought the problem may be related to light hitting the top layer of hydroton, or low DO levels, so I purchased some covers for the net pots, and added air stones to the grow bed. I tried removing the top layer of hydroton from each net pot, but the problem came back after about a week.
I've attached a picture of one of the net pots. I have noticed that the problem seems to the worst closest to the point where water enters the grow bed. I have several things growing here, strawberries, celery, cilantro, parsley, etc. Oh, and the water level comes just about to the top of the hydroton. Any suggestions to get rid of this problem?
That looks like minerals to me too.
Here just so you know you can use the image button (second from left on top of the text box) to put pictures directly in your posts so people don't have to click away to see what you are talking about.
The hard water is generally fine for most types of fish we grow in aquaponics, it is just in situations with huge amounts of calcium carbonate in the tap water you might wind up with very highly buffered water and a pH too high for plants to thrive. It is for those kinds of situations that Rain or RO water might be recommended.
Being an Aquaponics Site I kinda sorta assume fish unless stated otherwise.
I'm cautious about saying fertilizers are safe to use. I would be very specific about exactly what you used and at what concentrations. (People sometimes skim read and from your above post might pick up the wrong bits of info and then go dumping in a strong dose of something and wind up in trouble.)
Just as long as the people reading understand the appropriate H2O2 dilution or usage to keep from killing the bio-filter or fish.
Sorry for the slow response, but thanks for all the help everyone! I'm relieved to learn that it is mineral build-up rather than mold. (And thanks for the image tip TCLynx, I was wondering about that.)
This is an aquaponics system, I didn't even realize hydroponic folks were one this site as well.
As of September 10, the water quality in the system was as follows:
DO 11 ppm
Ammonia 0.25 ppm
Nitrites 0 ppm
Nitrates 40 ppm
Water temp averages high 80s to low 90s.
Right now I have 5 goldfish in there, but soon I plan to use this as a holding place for tilapia fingerlings. The fish tank is about 20 gallons, and the grow bed holds about 28 gallons of water.
The plants seem to be doing fine for the most part. Oregano and thyme don't seem to like this system for some reason though. Oregano grows well in my other flood-and-drain hydroton-based system, and I'll try the thyme there soon.
The mineral build-up seems to be slowly taking care of itself. I'm going to try raising the level of my plants slightly above the water level with another raft on top of the existing one.