Tuesday, June 2, 2015

I believe you can never learn too much when it comes to water chemistry and what keeps it livable for our aquatic pets.

Here is an excerpt from a forum that I thought would be interesting for those that need some enlightenment in the bacteria world of explanations. Though you may never use an Anoxic Filter, this microbial explanation of how the Nitrogen Cycle works and how and Anoxic Filter works is quite interesting. I believe you can never learn too much when it comes to water chemistry and what keeps it livable for our aquatic pets.

Originally Posted by Feline View Post
I think the issue with the nitrate would be that Bryan's current filters are consuming his ammonia very well currently producing nitrite and then nitrate as the end product. Adding a small amount of anoxic filtration would mean that SOME of the ammonia would be dealt with without producing any nitrate, so the overall nitrate would be a bit lower, but the anoxic filters can't actually take the nitrate made by the 'normal' filters and do anything with it. The anoxic filter would have to compete with the other filters for ammonia to use. Bryan's set up doesn't sound ideal as an only filter, so he wouldn't have the option of turning off the traditional filter.

Maybe Manky can explain for us which filter system 'wins' the ammonia when you have anoxic and traditional media competing for it?

That's a hard one Lara,

But I'll try to explain all your points and what I think will most likely happen when ammonia is shared between the two filters, starting with the basics. I'll skim over them just to avoid making this too long but I'll expand or explain any point if anyone wishes.

Conventional (nitrogen cycle) filtration, very, very roughly, takes one ammonia molecule, four oxygen molecules and seven carbonate molecules into the cycle and, after the bugs have done their job, there is one nitrate molecule excreted as a waste product.

Between the two main species of bugs we could say that, in round numbers, one ammonia becomes one nitrate.

Anoxic filtration is far more complex, and depends on the exact species of bugs and conditions in the basket, which is why I warned about altering the recommended design too much.

Biocenosis baskets attract ammonia in towards the Laterite. Bugs within zone C switch to (my favorite expression) the dimorphic metabolism of facultative anaerobic.......(yeah that one). They use the ammonia directly as a nutrient. Plants in planted baskets use ammonia as a nutrient. The Laterite also attracts in nitrate (NO3) and phosphate (PO4). Them facultative bugs also need oxygen so they steal it from nitrate and phosphate.

What all that means is that nothing comes out except nitrogen gas. Nitrogen gas is harmless and your pond is full of it anyway so this extra amount is gassed off just like excess carbon dioxide from fish respiration.

So that's a very basic overview of how each system works. I hope it also helps explain why conventional filtration starts with ammonia and ends with nitrate whereas a biocenosis basket takes in ammonia, nitrate and phosphate but only puts out nitrogen gas.

If you put a fully mature conventional biofilter alongside a fully matured (and full size, not just a few baskets) anoxic filter then I would need analyze some water samples to give a definite answer but it's reasonable to assume they would each take 50% of the available ammonia.

If a full size anoxic filter would require, say, 40 baskets but you only had four then the four baskets could only do 10% of what 40 baskets would do.

Put any 10% efficient filter, (anoxic or conventional), alongside a filter that could handle 100% and it would only take 10% of the available ammonia. The full size filter would take the rest and an anoxic filter in that situation could only make a 10% reduction in nitrate.

This might help explain why I had reservations about four odd shaped baskets just planted up with cat litter and Laterite. Baskets only work to 100% efficiency if they are built to Kevin's guidelines. Using the wrong size round basket or a kidney shaped basket will do no harm and, of course, there will be some degree of anoxic filtration but the question is how much?

Any reduction in efficiency cannot happen in zones A or B. Reduced efficiency will only occur in zone C, where my favorite bugs live. Even if you were lucky enough to only lose 50% efficiency per basket, put those four baskets alongside a fully mature conventional filter and, at best, you could get a 5% reduction in nitrate. You get twice that much reduction just by minimum normal water changes so is it true to say that the pond is benefiting from anoxic filtration?

To repeat, building baskets incorrectly won't cause any harm but I hope that helps explain why I say either do it correctly or don't expect any noticeable benefit.


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