Micronutrient buildup - is it a problem?

[Steve Robinson]

A couple months ago the nitrate level in the tank droped from the hundreds down to 20, and has stayed stable ever since.  I added red worms to each of the three beds maybe a month before that event, and had also added maybe a teaspoon of the seaweed extract every few days.  I also add a teaspoon of chelated iron every other week.

When the nitrate levels dropped, I figured sufficient nutrients had finally found their way into solution to allow the nitrogen to drop.  The tomatos just took off, and I was getting perfect 8 oz tomatos, basil, eggplant, and some really good romaine lettuce.

I have three grow beds with a total of 22 sq ft serving 25-28 tilapia weighing well over a pound each.  The grow beds are packed with plants and resemble cubic jungles of dense vegitation.  I say this to give an idea of the nutrient uptake capacity.

Now, ammonia level is flat at zero, nigrate = 20, pH=6.8.  All these values have held constant for the last 2 months.

Question:  When I feed the fish, they take what they need leaving their waste product which breaks down in such a way that the plants can grow well.  Now, the plants take what they need and probably leave unused nutrients behind that can I believe can build up over time.  Some of these nutrients can become toxic at higher concentrations.

Do folks have the experience of micronutrients build up?  What keeps this from happening?  If they do build up, what is the best way to handle the situation?

Thanks

Steve

[TCLynx]

Are you still adding the seaweed and chelated iron as regularly as you noted in the first paragraph?

I would say back off the dosing of the "extras" till you see a change.  You want to make sure you are only dosing as much as necessary and not more.  See in Hydroponics the nutrient solutions tend to be very concentrated and when the plants use up what they need but leave the rest and things get out of balance, they have to dump and totally replace their whole nutrient solution.  We don't normally do that in aquaponics but we also have to be careful not to go overdosing on things we don't actually need.

[Steve Robinson]

I probably still add every other week maybe that same amount.  I'll cut back from that.  I may also do a 50% water change just to be on the safe side.