To denitrify

[subsea]

The nitrogen cycle in reef tank husbandry is number one to be addressed by most "keepers of the reef". What to do with nitrates after the oxidation process has reduced amonnia to nitrite to nitrate. To accomplish denitrification with bacteria requires a "reducing enviroment" brought about by a decreasing oxygen gradiant in sediments or live rock. I wish to focus on sediments, because the concept of deep sand beds has created confusion because of termanology. I am not a scientist. I am an engineer that understands some chemistry. Because I was certified in municipal waste water treatment, I have some knowledge of denitrification as a large scale process. When we get into sediment science in our reef tanks, I must quote Martin Moe http://www.amazon.co...ader_0939960079.

As a Doctor of Philosophy in Marine Biology, Martin Moe was asked about the science involved in reef keeping in the early 1980, he said, "It is not rocket science. It is more complicated". The complexity of what goes on in our DSB sediments is illustrated in municipal waste water article labled "faculative lagoon". http://en.wikipedia....ultative_lagoon If you replace the water in this lagoon model with water in our reef tanks, then add a sediment water interface we call our deep sand bed. Well, you can see the analogy. In fluid mechanics, it is an engineering principal to group air, water, plastic and steel with the term viscosity. Each one of the fluids mentioned flows with a different viscosity, from the point of view of fluid mechanics. If you use the same analogy to describe sediments, then the common engineeering term would be size. Mud and clay is infinitely small when you compare to a boulder. Oolite sand, sand, crushed coral, pea gravel, gravel, boulders and mountains are the same but for size.

The reason that I focus on sand size is that in the methods that we choose to cover our tanks bottom determines colonies of different types of bacteria. I favor faculative bacteria as opposed to sulfide bacteria. Both perform denitrification but faculative bacteria are ten times more efficiant at the chemistry that they perform, according to Doctor Bob Goemns. http://www.saltcorne...Books/Books.php As an engineer, if I want to enhance the enviroment to multiply these faculative bacteria, then I look at their requirements. The one requirement which I can control is a reduced oxygen requirement. If the oxygen gradiant for a reducing enviroment is extended in depth, then viola, we have increased the denitrification bacteria population. Getting back to the sandbed, the highest water with oxygen is at the top of sandbed. As the water migrates down, bacteria consuming oxygen convert ammonia to nitrite to nitrate further reducing oxygen until the faculative zone. In this place, reduction chemistry converts nitrate to a free nitrogen gas molecule to be aspirated from the water. To extend the faculative zone requires a larger grain sediment to allow a further penetration of oxygen from the bulk tank water. As the oxygen gradiant is extended with depth, larger populatins of faculative bacteria are available to do denitrification chemistry.

[Bill B]

Hey Pat,

I do not pretend to understand some of what you described nor did I read your hyperlinked articles, yet? I do have two questions though. 1) How deep is a 'deep sand bed' ? 2) Could you say a little more on 'a larger grain sediment'? Are we talking 'sugar', coarse blasting sand, crushed coral .....

I'm sure this requires too large a change in my system at the current stage of recuperation but I am curious ... and always interested in what you have to say, if for no other reason than the way you say it, particularly in person

Thanks

Bill

[subsea]

Bill,

Good hearing from you. Look forward to seeing you at the next meetings.

With respect to how deep is a DSB, it depends on the grain size. Assuming that denitrification is the goal than1"- 2" of sugar sand (.1mm - 1mm), 2"- 4" of special reef grade (.5mm-1.5mm) and 4"-6" of crushed coral (1mm-5mm). I use the crused coral with a Jauber Plenumn. Now that I have mature sand beds and detrivores with janitors to clean my sandbeds, I do not even vacumn the gravel. Every now and again, I stir it up for the filter feeders.

Patrick

[subsea]

With respect to the larger grain size, the bacteria population is favored. When I use a Jaubert Plenumn with crushed coral for substrate I like to use a mud filter in the refugium for the most biodiversity of micro fauna and fana. Combine the mud filter with fast growing macro and you have a vegatable filter. The above combination allows nutriant export via nitrogen gas as the end product of bacteria, as well as, nutriant uptake and recycling from both plants and micro fauna/fana in the mud. In the case of numerous worms and other sand bed critters, their populations multiply as they feed corals and fish. This is nutriant recylcling. Feeding macro to fish is also nutriant recycling. Prune macro and composting tomatoes is nutriant export. For the above reasons I stopped using protein skimmers 10 years ago. I rely on herbivores to keep tank clean. I like my sand bed critters. When my grandson comes over, we spend quality time looking at the bugs and things with an illuminating magnifying glass.