Backyard Aquaponics
A place to discuss aquaponics

Hey Forum,

I'm still having some issues with my system. There is plenty of nitrate 40-80ppm, very little nitrite and ammonia, fairly stable PH of 6.3 yet my plant growth looks terrible. Very pale green-yellowish with the odd bit of brown spots. The fish look great though.

I'm trying to think about what is different about this system than previous systems of mine that have run fairly well (at least never this bad) and I was remembering that I dumped a big pile of activate charcoal/carbon into the system as a pile of it was given to me from a friend who shut down his big aquarium. He said it would make my pond smell less like a pond. I guess to an extent he's correct, the pond doesn't smell very pond like and the water is very clear, but maybe it has a negative affect on the plants?

Depends on what it was designed to target ie remove. I would just foliar feed with seasol for a while, it should soon become inactive and just end up as another place for bacteria to grow.
BTW what size was it and where did you put it?

It was probably 1 gallon of charcoal. I put it in in my bio filter, which is essentially a flood and drain rubbermaid, mixed with 3/4 inch gravel and hydroton.

Plants looking like you describe are suffering from some mineral deficiencies, probably iron and magnesium.

You didn't need to dump the charcoal into the system; it would have been better to keep the charcoal together in a container and run the water through it e.g. put the charcoal in a sock and place the sock over the end of the pump discharge, or the GB drain. It would be easier to control and/or remove.

Activated charcoal adsorbs impurities (no, it's not a spelling error of "absorbs", it's a completely different process) which is why it's really useful to clear up aquarium water, especially discoloured or tannin water. The size of the micropores on the surface dictate the filtering capability of the product, so different charcoal products can be used to target different pollutants. However, for use in the AP setting though, I'd steer away from it because of arguments which are yet to be completely proved or disproved, that activated charcoal filters can adsorb essential elements, especially if those elements are in chelate form:



Even if you added iron chelate now to correct the nutrient deficiency in your GB, the activated charcoal will adsorb it until it is "saturated" and then slowly give it back over time, in which case it's probably too late for the current crop. Adding iron in another form would not be readily taken up by the plants (hence the reason we use iron chelate) so would also be of limited use to remedy the situation in the GB now.

I'd be removing the charcoal and adding some trace elements to correct the deficiencies in the short term, and continue to use quality fish feed to provide a balance of the essential elements in the long term, maybe supplemented with an occasional splash of seaweed extract as a general pick-me-up tonic for the plants.

Sorry I mean't what sized bits was the activated carbon. If its very small it could eventually clump together and leave you with a problem.
That's a lot of activated carbon

Wow, excellent advice guys. I totally agree, it does seem like it's lacking in other minerals. I will put some seaweed into the system.

I'm curious, do you think it would be a good idea to feed my fish (mostly goldfish and koi, but some minnows too) any kind of blood meal? Maybe blood worms or something? I spent all evening digging out the whole bio filter and now starting fresh with mostly hydroton.

Can't say they need bloodworms, although mine get caterpillars from time to time Frozen baby peas warmed up and popped out of the skin are good occasionally (keeps them regular)

It's not the activated charcoal, add some Maxicrop/Seasol. The pH is pretty low are you sure it isn't actually lower than 6.3, which may be locking out nutrients. That amount of charcoal may bind up some nutrients for awhile until it is saturated but they don't disappear from the system forever. What is the size of the system, compared to the gallon of activated charcoal?

It's not lower than that. At least my PH pen which was just recently calibrated and my test strips don't appear to say so. The system is about 100 gallon, in which about 1 gallon of activated charcoal was put in, and the charcoal was brand new from a Fluval (the brand) jar.

I've since removed the activated carbon and did a 90% water change and the plants appear to be recovering already. I'll know in a few days time for sure. Thanks for your help everyone.