Anoxic filtration

[Steerpike]

Any thoughts on starting anoxic filters with fishless cycling? Will it work in a similar manner to conventional filters?

[Manky Sanke]

In all the years I've been promoting anoxic filtration, I can't remember anyone ever asking that question before but, yes, you can fishless cycle an anoxic pond. I've written up how to fishless cycle conventional media for my website on the link below but, with a bit of thought, you can adapt that process for the larger volume of an anoxic pond by isolating it from any through flow of water and with a few air stones strategically placed to keep the water circulated within the anoxic pond itself There is also a link to the detailed anoxic article I've written in case you haven't already seen it:
http://www.mankysanke.co.uk/html/fishless_cycling.html
http://www.mankysanke.co.uk/html/anoxic_filtration.html

[Steerpike]

[Manky Sanke]

Have you read my anoxic article on the link I gave? It gives all the information you would need to build an anoxic system including an explanation of exactly what happens to ammonia.

[Steerpike]

Yes, I have read it many times and would not have gone down this road without it!
What is puzzling me and I am trying(badly) to ask is will the filter go straight into that cycle or , like a conventional filter, will it develop in stages with spikes in nitrite/nitrate? Also will it take longer to develop than a conventional nitrogen cycle?
All the examples I have seen are adding anoxic to a already running conventional system not starting up from a new pond situation.

[Manky Sanke]

As it matures, the anoxic system doesn't go through "new pond syndrome" with an ammonia spike followed by a nitrite spike because the two bacteria involved in that process (nitrosomonas and nitrobacter) are obligate aerobes which means that they can't live without an oxygen level of at least 2 mg/L and oxygen levels in the baskets quickly fall to below that. The only bacteria that can survive in those conditions are facultative anaerobes (facultative anaerobic chemolithoautotrophic bacteria) and they turn ammonia straight into nitrogen gas (N).

Some people have reported rapid maturation but I advise that chemistry/biochemistry in an oxygen depleted environment will be slow so maturation may take longer than would be expected with conventional biofiltration.

[Steerpike]

Thanks again. You have confirmed my suspicions and the evidence so far seems to back that up- ammonia slowly reducing but little or no change in Nitrite/Nitrate. Plus overall taking longer than you would expect to mature fully given water temps well over 20C. Patience it is then

[Steerpike]

Thought I would give an update for any anoxic start ups.

The pond is 20000L and has 20 anoxic baskets, I am running the whole system for fishless cycling.

I added 200ml of 33% Ammonia on 30th May, this took Ammonia to 0.3. Nitrate was testing at 0-10. All tests with palintest tablets. Water temp 20C.
I then was away for a week, on return (12 June) Ammonia was zero, Nitrite 0.2 and temp 20.4C. Added another 200ml 33% Ammonia also 2.5kg Bicarb as water is very soft KH 30-50.

Ammonia reduced steadily over next 7 days and started adding 10ml per day from 20th June. Nitrite hovering around 0.2, temps now over 25C.

Ammonia maintaining at zero after 24hrs, By 29th Nitrite has climbed to 2.0+.

By 4th July Nitrite starting to fall, tests bouncing around 0.2- 0.5.

7th July decide to double the Ammonia added to 20ml/day to make more Nitrite and test system harder.

8th July Ammonia still zero after 24hrs, Nitrite testing up to 0.5- 1.0.

11th July Nitrite falling back to 0.2

12th-15th July Nitrite down to 0.1/trace. Nitrate testing at 10.

So I am happy that pond is ready for fish after 7 weeks of cycling, albeit at good temperatures , Nitrite wont quite drop to zero but I am told this is not unusual in new ponds. The Nitrate level has barely changed with 800ml of 33% Ammonia going in and no water changes other than topping up evaporation.
It does seem that the dreaded Nitrite spike has still occurred even in a fully Anoxic system?

Not very scientific but I hope my experience may be of some use to others.

[Manky Sanke]

The nitrite isn't being made by the anoxic baskets. Conventional nitrifying (nitrogen cycle) bugs are prolific in nature so there are ammonia bugs (nitrosomonas) which have already taken up residence on any wet surface in your pond. These will have begun to convert ammonia to nitrite which is what you are seeing. Nitrite bugs (nitrobacter) will develop later to take advantage of that and they will convert the nitrite to nitrate which the bugs in the baskets will remove in order to obtain the oxygen the nitrate (NO) contains.

However, as the bugs in the baskets develop, they will use so much ammonia that there will be little left for the ammonia bugs so their colony size will reduce and so will the nitrite they are currently producing. This is what you are seeing with the initial ammonia and nitrite spikes which have now reduced to a trace level without a corresponding high nitrate level.