magazine

[Triggerman]

for anyone interested in some good reading, the new marine fish and reef usa 2004 annual is now available. it has some very good articles on clams, coral diseases, sand beds, lighting, etc. by all the big wigs in the marine scene. it's a very good magazine for only $7.00 that comes out only once a yr., i know cb pets had them for sure.

ray

[Triggerman]

just read the article on sand beds and their benefits and recommendations. i can already see the controversy the author is going to cause between hobbyists since there are so many advocaters of deep sand beds. he basically recommends a 2-3" bed not neccesarily using all sugar grain size such as aragamax or southdown but a lg. araganite grain size since it has more bacteria benefits. there's really know evidence that a 4-8" bed better serves in denitrification better then a shallow 2" bed since most of the fauna lives in the upper 2" of the sand bed creating most of the denitrification.

i myself like a 2-3" sand bed using a mixture of grain sizes. i really never got into or believed in the whole deep sand bed idea using just sugar size grains. it's just my opinion but a 6" bed or larger is wasting valuable tank space. now don't flame me for my beliefs.

ray

[GaryP]

I'm with Josh on that. The smaller the particle size, the more surface area you would have for bacterial substrate. Yes most of the bacterial action is taking place in the first 2-3 inches, but that bacterial action is necessary to get the low oxygen levels necessary for denitrification at the lower depths. The first few inches act as an oxygen scrubber. Aerobic baterial metabolism will always be faster than anaerobic metabolism, but low oxygen levels are necessary for the bacteria that do the denitirifcation step in the nitrogen cycle (NO3 to N2O and N2). Also, coarse sand will tend be better oxygenated than fine sand and therefore would require a deeper sand bed than fine sand to reach the lower oxygen levels that are required for denitrification to occur.

Gary

[Triggerman]

at lower depths in a deep sand bed you have an anaerobic area and denitrification can take place if nitrate reaches this area. denitrification and nitrification occur almost simultaneously which means denitrification is most likely to occur close to where nitrification takes place and that's at the surface of the sand, low levels of oxygen can also be found in lg. areas of the sand especially at night. as for the grain size i also agree the smaller the grain size the greater the surface area which grows more bacteria, this is true if sand grains are perfectly spherical. as the grain sizes increase they're no longer spherical and you need to take in account surface roughness. so a fine sand bed offers no significant advantage over coarser aragonite sand in regards to bacteria densities. the easiest way to imagine this would be to think of the grains as miniature liverocks. like i said this is a very interesting article and kind of controversial, but studies are here to back it up.


ray