Backyard Aquaponics
A place to discuss aquaponics

I have just taken over the experimental aquaponics system at work and it is in rough shape, pH is way too high as is ammonia. I added lime to the system to fix the pH but when I mentioned the possibility of adding more biofilter media (shade cloth netting) my co-worker said not to and that would make the ammonia issue worse. His reasoning is that if you add more then you starve the colony of bacteria to death leading to a fatal ammonia spike. I have been studying aquaponics for nearly a decade and I have never once heard of such a thing, is that really an issue or is he just pointing a finger at the wrong cause of a fish kill?

Hmm, well I wouldn't be concerned about adding more filtration but there are some other considerations. One of the first things I would look at is if the ammonia is really toxic and this will depend on the pH and temperature of the water. This ammonia toxicity chart should help with figuring out if you're in the toxic range - http://ibcofaquaponics.com/information/tables-and-charts/

If you have netting for the filter right now and the system has been neglected, then you may not need additional filtration - you may just need to remove the existing netting and clean it with chlorine free water. As bacteria and other organisms grow they can cause the filter to go anoxic.

Post back about the fish load and the system (beds and other filtration) and I'm sure someone will have additional information.

I think your co-worker is a bit twisted. I can't see how adding more filter material can starve the bacteria.

The system is a 600gal total volume DWC system with a rather ineffective solids separator followed by a biofilter (both 55 gal barrels) containing tightly woven shade cloth netting it is about halfway full of this loosely packed netting material. We have about 12lbs of "salty" goldfish consuming 4-5 heaping tablespoons of floating fish feed of an unknown protein content, I did not acquire any of this and the person who did apparently did not care to ask. The system is in a heated greenhouse so extreme cold is not a concern. The grow bed is about two square meters currently growing a variety of leafy greens and herbs, although the extreme pH has left them with tip burn and most needs to be replaced. I have not yet removed the netting media because they said last time they tried to clean out the system all of the anoxic bacteria that they released doing so killed all of the fish. I would post pictures but it is a secure facility so no personal cameras or phones allowed and any sanctioned pictures would require permission for a press release. Nitrates read 5ppm and ammonia was off the charts although I think there is another chemical interfering with that test since 8ppm+ would have already killed everything in the system.

Adding lime will raise the pH higher. Having anaerobic areas will also raise the pH.
I'm not surprised it has high pH!
Clean the filters and drain to the dirt garden, beware it'll be stinky.

Sorry I said it wrong, the pH was shockingly LOW not high, when I took over it was 4.7 which I have brought up to 5.7 over the course of the past two days, the goal is to get it in the 6.5-6.8 range this week. The plant roots are covered in a thick layer of solid waste so I know I need to rework the mechanical filtration, I think the way they have it plumbed is allowing the waste to bypass the netting. They have the pipe coming in through the side of the barrel rather then the bottom leaving a gap without any netting allowing the water coming through to bypass the netting, the solids getting though to the grow bed are so bad that the bottom looks like mud. If I had materials to modify the system I would but all I have is a few pvc scraps to work with and zero budget.

Like any filter, once blocked the water or air will take the easiest path and find a way around it. Buckets overflow eventually. I think once you have cleaned it it will work. Better.
The thing with stand alone filters is they need regular maintenance. More work.

Stop feeding fish they can go a long time without feed until you are on top of the ammonia

Can you draw a diagram of the system

Don't try and do a cleanout while system is running switch system off or bypass filters

I would just tip every thing out of the filters give it a good wash and refill that will help short term , bacteria is every where in the system so will just recolonise

The DWC is probably in need of a cleanout as well

Partial water change to get on top of the ammonia

Look for other sources of ammonia (dead fish , uneaten feed)

I have set up temporary fish net / shade cloth filters to help through times of high feed consumption a few times now .

I put a storm water pipe in the middle of a 500L tank with notches on the bottom , inflow went into this pipe down to the bottom and up through the filter mesh / cloth , worked really well .

You will need to rework system to clean water up if you want to grow anything useful , so maybe a couple of scraps of pipe down into the barrels will work for now .

Already done a partial water change when I first saw that 4.7 pH and I left instructions that fish were to be put on half rations until pH was back above 6.2 where proper breakdown of ammonia and nitrite can occur, nitrosomonas and nitrobacter bacteria seem to be inactive at low pH. Looking through the log I saw that the system had been running scary low pH and high ammonia for months.
I am trying to think of a way to bypass the biofilter so I can remove the netting and clean it without stirring up so much sludge that I kill everything in the system, I know for a fact that the biofilter has never been cleaned out. I might put the fish on a fast for a couple days and allow the pump to just pump back into the fish tank for a bit until I can clean out the rest of the system and fix a couple of issues, should only take a few hours I cannot imagine that would hurt them if they are not giving off a lot of ammonia.
The purpose of this system is to test the viability of aquaponics in a prison setting, hence the lack of any kind of funding, that is also why I cannot take pictures of the system. My unit has been pioneering aquaponic and hydroponic production for a while now and the rest of the prison systems around the country are watching. So needless to say I am under just a bit of pressure to get this right. We had a much larger aquaponic system that was converted to hydro after a fish kill, since then most of the focus has been on hydro and I am trying to change that.

Once you get your Ph stabilized some of your trouble will be resolved

Whats your water temperature bacteria hate it cold and low Ph

If you had these with a clogged filter you may have had the perfect storm

Below is a bit of stuff I saved in my files might help you

Biological Data

There are several species of Nitrosomonas and Nitrobacter bacteria and many strains among those species. Most of this information can be applied to species of Nitrosomonas and Nitrobacter in general., however, each strain may have specific tolerances to environmental factors and nutriment preferences not shared by other, very closely related, strains. The information presented here applies specifically to those strains being cultivated by Fritz Industries, Inc.

Temperature

The temperature for optimum growth of nitrifying bacteria is between 77-86° F (25-30° C).

Growth rate is decreased by 50% at 64° F (18° C).

Growth rate is decreased by 75% at 46-50° F. (10 C)
No activity will occur at 39° F (4° C)

Nitrifying bacteria will die at 32° F (0° C).

Nitrifying bacteria will die at 120° F (49° C)

Nitrobacter is less tolerant of low temperatures than Nitrosomonas. In cold water systems, care must be taken to monitor the accumulation of nitrites.
pH
The optimum pH range for Nitrosomonas is between 7.8-8.0.
The optimum pH range for Nitrobacter is between 7.3-7.5
Nitrobacter will grow more slowly at the high pH levels typical of marine aquaria and preferred by African Rift Lake Cichlids. Initial high nitrite concentrations may exist. At pH levels below 7.0, Nitrosomonas will grow more slowly and increases in ammonia may become evident. Nitrosomonas growth is inhibited at a pH of 6.5. All nitrification is
inhibited if the pH drops to 6.0 or less. Care must be taken to monitor ammonia if the pH begins to drop close to 6.5. At this pH almost all of the ammonia present in the water will be in the mildly toxic, ionized NH3+ state

Thanks for the info, I already knew that my bacteria quit working in acidic conditions but I did not know the exact range. I don't actually know the water temp of the system, have not worried about it being in a heated greenhouse. I would guess they keep it 77-80 degrees in there, warm enough that I start sweating just a little when I walk in. I am debating on pulling all of the greens and herbs in the system currently, roots are a fish poo coverd mess the leaves have tip burn and I don't think any of that will clear up, everything is looking really bad except the bok choy which somehow is thriving in conditions that have left everything else dead or wilted. That appears to be some tough stuff.

Put a high/low thermometer in the greenhouse and see what the temperature extremes are for certain.