Backyard Aquaponics
A place to discuss aquaponics

for... converting ammonia and nitrite into nitrates?

i.e. For a mature system with a well-established bio-filter, what is the maximum rate, in ppm, can the bacteria convert ammonia and nitrite into nitrate and in how many hours? Can it be measured by "ppm per hour" ?

How much ammonia could be converted per hour would be totally dependant on the (size) amount of filtration capacity available...

Not sure what you're getting at... we would normally measure filtration capacity by volume/hr

Do you mean the ratio of grow bed to fish tank?

If so what is the common ratio used? I thought it was 2:1 (growbed : tank) My ratio is 1:1 not counting the sump.

I'm also guessing it's needed to take into account other factors like type of media used and water parameters. But there's gotta be a narrow range of average for ideal conditions.

Also, any idea how long it takes for a system to "mature" ?

I'm not sure about the ppm of ammonia that it can handle per hour or whatever but if you are wondering "how much fish can a particular amount of media support?"
Then the answer is like 1 lb of fish per 5 gallons of flood and drain grow bed or 3 kg of fish per 100 liters of flood and drain grow bed.

Now I suppose you could look up some things and work out how much food to support that amount of fish and how much ammonia that would produce and know that generally if being run properly and noting goes wrong/spikes, we don't see ammonia/nitrite readings normally so therefore, that amount of gravel can process however much ammonia that amount of fish feed/respiration produces in a day.

Does this help answer your question at all?

Confuzzed,
I think you are trying to quantify something that is too complex to simply put into "boxes to be ticked" to allow you to quantitatively design a system purely around flow rates and bacterial conversions, especially for the simple, natural systems used in AP, and have been so for thousands of years.
You would have to know how much Ammonia ( by volume? cu.mm. perhaps?) each Nitrosoma can consume per hour/minute/second and under what temperature and what matching pressure (if submerged or not), to produce what ammount of Nitrite. 5 unknowns and 2 variables that could only be laboratory controlled.
You would then need to quantify how much Nitrite each Niterbacteria can consume per time interval, under the same conditions, to produce what amount of Nitrates. Again 5 unknowns and 2 variables.
You would then have to correlate that against how much surface area was required to support each type of bacteria to do the conversions if acting at full capacity and what the available surface area was of the proposed supporting media to gauge a volume to be effective.
You would also have to take into account that all these processes are happening concurrently, interactively and not mutually exclusively. In fact, anedotal evidence definitely points to the Total being greater than the sum of the parts. There are many other interactive processes going on with Ammonia, Nitrites and Nitrates that I don't even know how to explain which reverse these reactions as well as accelarate them, perhaps Rupe can help me out?

You would then need to take into account the amount of the bacteria which is contained in the recirculating water and whether that contributes to pre-processing of nutrient by the attached bacteria on fixed media. It has been found (UVI research) that there is more bacteria in the water than on the media of any type of bio-filter in any recirculating system.

And that is just for free Ammonia from the 75% of dissolved fish wastes. The other part of the equation is the treatment/mineralisation of the 25% solid fish waste. This is where the natural Bio-filter comes into it's own. The small gaps between the bacteria laden gravel media physically filters out the solid matter, holding it in place for it to be acted upon by other forms of Bacteria (and worms! but then you have to get rid of their solid wastes!) This action is always anaerobic and can cause dead spots in your filter media unless you can get oxygen to it etc. This process, acting side by side to the aerobic processes would also have to be taken into account to gauge the detrimental effects on the Good bacteria converting Ammonia not only from the fish waste, but from the anaerobic activity next door!

I think you are paddling a barbed wire canoe up shite creek without a paddle if you think you can quantify all these things that work well enough on their own if just given time to reach a balance and settle down by themselves.
Trying to cycle quickly and attempting to hasten any natural process for no good purpose other than you can! puts you in the same boat (to me!) as people who want to Genetically Engineer plants to satisfy the apparent need for instant gratification that the world seems to be suffering from to-day!

Let the system work itself out. Maintain a balnace. If you add something here, you must take something away there!

My two bits worth.

Cheers IanK

Not quite TC, but what Ian said.

Nevermind this question

I don't know if it could be measured by ppm per hour and I am not sure if that would be the best way to approach the question.
A mature bio-filter is one that has established colonies of both types of bacteria and is converting the ammonia into nitrates- this is the same process, whether we are talking aquaculture or aquaponics. This can be reached in as little as 2 weeks (some have said) or as long as several months (excessive ammonia) but the average, with moderately ideal parameters, is about 6 weeks.
Now a mature aquaponics system is another subject- that takes 6 months to fully mature. Apparently, there are other types of flora and fauna that continue to mature and they are extermely beneficial to plant growth. Researchers are still trying to find out what is causing this phenomenon that makes aquaponic systems jump ahead of hydroponic sytems in regards to excelled plant growth.

Now in regards to a bio-filter's maximum capacity, this is usually based on the size of the filter, the filter's medium (living area for the bacteria) and feed conversions (with higher protein feed requiring more filtration). This is actually a better way to size a system as you want to plan the maximum fish carrying capactity. Once you establish the maximum number of pounds of fish you will have, the feed conversion rate for the species you're growing and the protien content of the feed, the bacteria formula is pretty cut and dry. The formulas posted below are for daily feeding rates so you can break it down to hourly or to minutes, if you chose but remember that most here feed once or twice daily so there is more activity at that time and it will impact DO as well as other parameters.
There are 454 grams to a pound.
Another formula that I use is to figure the Total Ammonia Nitrogen Production Rate (TAN) and work from there. (Please note that the original formula was written in metric so my formula has been converted to Imperial Standards.)
.065 * 2.2046 * pounds of feed per day * feed protein content


SRAC Publication No. 454 Recirculating Aquaculture Tank Production Systems: Aquaponics—Integrating Fish and
Plant Culture
The waste treatment capacity of raft hydroponics is equivalent to a feeding ratio of 180 g of fish feed/m2 of
plant growing area/day. (Note: 1 m2 = 10.76 ft2 and 454 g = 1 lb.) This is equivalent to about 1.2 pounds of feed for each 8-foot x 4-foot sheet of polystyrene foam.
As a general guide for raft aquaponics, a ratio in the range of 60 to 100 g of fish feed/m2 of plant growing area per day should be used.
Gravel and NFT systems should have a feeding rate ratio that is approximately 25 percent of the recommended ratio for raft hydroponics.