Confusing article - need clarification

[Eng Keat]

Hi,

I'm reading the FAMA July 2003 issue and came across an article replying to an aquarist facing hair algae(Pg 50). In the article, it is mentioned that

1) denitrification process in anaerobic areas, nitrate is only reduce to ammonium (a nitrogen compound).
> Is the above statement true? If yes, what effect ammonium had on the system?

2) nitrate is fully broken down in anoxic areas

3) anything much over an inch or two of sand and/or overabundance of LR is a good breeding ground for alga nutrient
> Am I right to say that in order to obtain pt(2), you need at least 4 inches of DSB. If that is the case, is pt(3) true?

4) it is bad idea to cover more than 25% of the sandbed surface with rocks
> How can we obtain the proportion of 1/3 to 1/2 tank area without covering 25% of the sandbed surface?

Eng Keat :roll:
Thanks

 

[Anonymous]

Boy, let's see if we can pick this stuff apart. I'm also going to point you towards our onsite library ( http://www.reefs.org ) as well as trying the VAST database found in our online 'zine--Advanced Aquarist (lots of links on every page for that). Also, try http://www.wetwebmedia.com for more information on natural nitrate reduction than you can shake a stick at.

First things first (wish I had the FAMA here in front of me, but oh well).

1: Nitrate is the last byproduct of the nitrification cycle, that being the cycle by which different species of bacteria break down ammonia first into nitrites (via oxidation, if I recollect the chemistry correctly), and then into nitrates. Ammonia, therefore, cannot be the end result or byproduct of nitrates (well, by my line of reasoning at least ). Ammonia is very toxic to fishes and invertebrates.

2: Yes, nitrate is fully broken down into its components (much of which is nitrogen gas--approximately 80% of earth's atmosphere is comprised of this harmless, inert gas) only in the anoxic/anaerobic regions of live rock or a deep sand bed.

3: There are varying opinions on the utility of the deep sand bed, however, rereading the just-released book "The Natural Marine Aquarium--Reef Invertebrates" reminds us that, in order to be at all effective, a deep sand bed (DSB) must be at least 3" in depth (4" or more is better, in my opinion), and once this is established, especially in concert with good quality live rock your system will experience the benefits of natural nitrate reduction. Excess nitrates are just one of the reasons one will experience nuisance algal growth. Phosphorous is another, and inadequate nutrient control is another (dissolved organic compounds). This is why I like to recommend the use of refugia in concert with a DSB, in which macroalgae can be grown, thus outcompeting nuisance algae for nutrients. This can then be harvested to directly remove nutrients, or harvested and fed to animals such as tangs. Also, please know that many Tridacnids (including Hippopus spp.) and other bivalves can help in this nutrient control. I would not use foam fractionation on such a setup, in order to keep the plankters that other animals will feed upon. (Whew!)

4: We do not like to rest rockwork directly onto any substrate, but rather prefer to either place the rockwork in before placing the sandbed/substrate, or even elevate the rockwork. There are many clever ideas for this, I've seen some put up pics of rockwork that is elevated with acrylic rods (quite the cool feat), or even just PVC that's been drilled to allow water flow. Once you've got things set up in this manner, I wouldn't worry about what percentage of horizontal tank area is covered with rockwork. Besides, if you use the 1-2lbs. of rock/gallon of volume rule, you are going to be very hard-pressed to NOT cover up a significant area of the tank bottom.