Water Turnover

[Ravnis]

maybe we need an "advanced aquaponics category". I enjoy seeing the formulas, even though I may not fully understand them. Google is a good friend to look up acronyms such as TAN.

A question is do the formula's take into the account the direct assimilation of ammonia and its byproducts out of the system by the plants?

[Crusty]

A question is do the formula's take into the account the direct assimilation of ammonia and its byproducts out of the system by the plants?

Good question. No the the formula do not take into account anything the plants may do as it will be very small depending on the plant species and I always include bio filtration as it is easier to calculate capacity and the nitrogen in nitrate form is proven to provide better growth. Keep in mind that ammonia is toxic to plants especially if the ammonia:total nitrogen stored is greater than 1:5 (20%). Even when ammonium fertilizers are used on land crops it is in combination with other nitrogen sources and it is converted to nitrate in the ground and why not much is used in winter as the nitrogen cycle is much slower so ammonium is avoided because of its toxicity especially in low pH. The fact ammonia is potentially more dangerous to plants at low pH and more toxic to fish at high pH, makes for interesting discussion around the ideal pH.

[Ravnis]

Interesting. So what phenomenon is taking place when the system has ammonia and nitrite spikes when old crops are removed and replanted? I have observed this several times now to make me think it was the plants taking the ammonia directly out of the water and as new growth replaced the old growth; the levels dropped back down. The first few times I thought it was a fluke, but I have repeated it a few times now as I have tried different types of plants in the system.

The ph thing and ammonia is quite interesting too, because it is my understanding the ph difference changes the ion formed in an aqueous solution. In this example ammonia vs ammonium.

[Crusty]

As I said the plants do take up ammonium, it is not a phenomenon. I can't speak for your system Ravnis as I do not know what it is. If you are using a media based system without solids filtration the ammonia spike may be from the increased heterotrophic activity and due to the sudden increase in ammonia the nitrobacter will have been inhibited and a nitrite spike will be the result. Disturbing a grow bed, will dislodge organics, which in turn deplete oxygen which in turn inhibit the nitrifying bacteria. Who knows..?

It is my understanding that ammonium is a positively charged cation and uptake by the plants produces H+ (pH and alkalinity downward), nitrate is negatively charged anion and uptake by plants produces OH- (pH and alkalinity upward). Something to do with denitrification. But I could be completely wrong.

[GaryD]

While it doesn't alter the thrust of this thread, it might be of interest that duckweed will take up ammonia.....in its un-ionised form.

If you have enough of it, it could serve in a bio-remediation capacity........and jade perch will eat it quite happily.

Gary

[ash33]

Do the above priciples hold true for flood & drain systems or are they specifically aimed at constant flow systems?

If for instance I had a flood & drain system with a total capacity of 10,000L would I still need to circulate 10,000L per hour?

Secondly, if it takes my system 1hr to circulate 10,000L via 5 grow beds with 1 x 25mm standpipe in each bed at 2000LPH (max theoretic flow rate is 2340LPH accounting for fiction loss etc.), can I use more than one Bell Syphon per bed?

Lastly, should there be a down time or no pumping cycle between flooding the beds?