Backyard Aquaponics
A place to discuss aquaponics

After 18 months, I seem to have a steady supply of Nitrites. I'm using a MT and reintroducing water as well as feeding the fish a lot more then I used to. Now, is there an optimal level that I should try and keep the N level at? Growth all looks very good, but could it be better? I don't know, due to not experience with these crops. Also, I'm growing so many different crops, is there a compromise number for greens and flowering plants?

Right now- Toms, peppers, cukes, strawberries, chard, lettuce, broccoli, kale, amaranth, and I think I'm missing a few. My Nitrites are right around 80, but I seem to be able to loosely control by increasing feed rate and more adding MT water more frequently.

I know Ryan will have more info in his commercial course, but I don't want to wait until April/May to find out. I guess my patience is still not too good.

Hi coachchris,i take it you mean nitrates not nitrites,anyway from my systems i ran the nitrates up to the 100 mark but have now dropped them right back down closer the 20 mark,in my opinion growth is better at the lower figure,unless i learn something new i will aim to keep them below the 40 mark at all times.

Yes DB, yes nitrates...I thought I checked the spelling before submitting. I can allow the shade cloth filter to go longer without cleaning, and will start to see denitrification. Just not sure how long it will take to drop down to the 40 range. I can also slow down the feed. Thanks

From my reading, tomatoes will produce more if they have a higher nitrate level to start off with, then when they get to a certain size (about to start fruiting), knock back the nitrates to 20 or so.

I think leafy veg do better at a high nitrate, but I'm still playing catch up there. Still no nitrates in my system. My fish need to breed already.

coachchris i have improved my denitrification by changing the shade cloth over to bird netting,i don’t know why this should be as i didn’t change it for this reason the main reason is i think its easier to clean than the shade cloth,but now biweekly cleaning sees my nitrate at 12.5mgl.

I have lots of shade cloth, and no netting. If I can find some netting for reasonable, I'd like to try it. Thanks Andy.

Solids accumulation isn't the driving force of denitrification.. nor is lack of oxygen in an environment... denitrification is not a chemical process but is a biological process in which the microbes are scavenging for 'free oxygen atom' denitrification can actually happen well in a fully aerated system and filter.. what promotes denitrification are the number of microbial growth in the filter.. when this increases them the demand for oxygen increases to a point where nitrates are used up as well.. to speed up the process an additional carbon source is add to promote faster bacterial growth which inters increases denitrification. but its a very risky process because denitrification causes nitrite spikes due to nitrite being an intermediate product in going to nitrogen gas.. and well nitrification also produces nitrite as well in going to nitrates.. so constant monitoring is always advised.

My take on Denitrification.
It can only occur in anoxic conditions,so in oxygenated systems it occurs when we get solids build up,where the oxygen level falls below 0.5mgl.
The Hetrotrophic Bacteria responsible, obtain there oxygen from Nitrate [NO3] leaving nitrogen and nitrogen compounds and there food source from organic carbon,when the amount of these bacteria grow rapidly due to an increase in solids we see a reduction in autotrophic bacteria ,an increase in the production of CaCO3,which leads to PH rise and eventually system crash.
In a oxygenated system but with anoxic areas adding a further food source for the hetrotophic bacteria would just hasten system fail,the only time you would add a carbon source for denitrification would be in a true denitrification filter.
Hetrotrophic bacteria are not good things to have in excess in our systems,they grow faster than the autotrophic bacteria,taking up valuable space required for nitrification,hetrotrophic bacteria are excellent at breaking down ammonia but if they are in high numbers compared to the autotrophic bacteria which are required to complete the process they will release organic matter back into the system. One of the reasons we need large media beds to cope with amount of solids we put into them.

When you clean your Bio filter you kill the bacteria right? So it would make sense not to clean as often.

No, and it depends.

First of all why do you need a dedicated bio filter? In AP you generally don't. Your single GB is more than large enough to provide biofiltration for your one IBC FT.

If you are going to have a dedicated biofilter why does it need cleaning? If it does need cleaning why does it need anything more than a backwash? What is going wrong that you need to do this?

If you biofilter does need cleaning because it is clogged then you have other probelms that are more pressing. Throughly cleaning it with I don't know hot water and a pressure washer will kill a whole stack of bacteria but since AP systems have masses more biofiltration capacity than they need then the effect on the system will be minimal.

If you biofilter does need cleaning because it is clogged then you have other probelms that are more pressing.

+1,if your cleaning for this reason your nitrifying bacteria have already started failing,hence the need to clean it so actually cleaning it can only improve the situation,remove it,hose it off,put it back and fill with water and by hosing it gently you should still leave bacteria on the media to restart the process,hopefully it will just be a knock back and should start building back up quickly.

But let's not forget that nitrosonomas (nitrifying bacteria) are very slow producers, whereas introspira are very rapid and double quickly. My experience and thoughts have always been that frequently washing biomedia incorrectly could have a negative effect on overall biological filtration and stability of that filter, rendering it less inofficient of its purpose. Even the UVI models didn't have a very discript cleaning process and I havnt seen anything educational stem from copy cat models. I think more study needs to be done which is happening through the mineralisation thread so it's good to see some brains come together.

+1

There is a balance that needs to be struck. These organisms are everywhere in nature so it's not like you'll be ridding yourself of any that you don't want so you have to find where the filter functions the best for what you are trying to do. That's what will determine the cleaning frequency.

A simple backwash shouldn't do anything to knock a bio filter around. I really believe that the concern people have over bio filters is so over blown and I struggle to understand why they get so much attention.

What I keep coming back to is that so many of the "new systems" that we are seeing a being overly influenced by Aquaculture methodology where bio-filters are often one of the limiting factors on capacity.

In almost all cases Bio-filtration capacity is so much more than what is required that it is not worth taking any time to think about. In the UVI system one of their research aims was to demonstrate that a dedicated bio filter was not necessary. What they found was that as long as they didn't harvest ALL their plants at once then there was enough surface area on the plant roots to more than supply enough habitat for bio-filtrating bacteria.

Another reason I think that people focus on bio-filtration is that it is "cool" or at least cooler than focusing on fish poo which is where the effort in design, brain power and capacity really needs to go.

Rackocy actually increased the amount of solids filtration they used,but interestingly although the solids from the clarifiers was mineralised further it was not added back into the system but used as farm fertiliser.