[s1214215]

Hey Reeflanders...

I am moving soon. I want to put oolitic sand in my tank as a base rather than crushed coral which I think is trapping nutrient in my reef tank and thus may be why I cant get my nitrates below 5ppm and my phosphates below .25. I have a 7 inch deep sand bed (45cm x 45cm) in my refugium with lots of assorted algaes (red, green and browns). I have gotten rid of the noxious green algae on the glass from my system (1 year old) but seem to still get some cyano-bacteria.

I have no idea if the sand in my DSB is calcite or Aragonite - will check with vinegar to see (just discovered this test). I can only get this one oolitic sand here in Thailand and they say its beach sand (so it could be anything from the mountains to the sea LOL). The question is, can I use this sand without any major problems if I find out its not aragonite? I will have to replace the sand in the DSB when I move. I wonder is there is nutrient in the sand and thats why I am still getting cyano. Or could it be the crushed coral trapping nutrient even though I have lots of water flow? I need some advice please

[kevinpo]

Crushed coral will still trap nutrients even with very high flow. You can still use crushed coral but in order to prevent cyano you will have to keep it clean using a gravel vacuum. It is a large diameter tube (1" x8") with a smaller tube attached to the back of it. When you siphon water out you push the large end of the tube into the crushed coral. It lifts the crushed coral a couple of inches and allows the smaller lighter particles to flow up and out.

Regards,
Kevin

[Ninong]

Originally Posted by s1214215

I have no idea if the sand in my DSB is calcite or Aragonite - will check with vinegar to see (just discovered this test). I can only get this one oolitic sand here in Thailand and they say its beach sand (so it could be anything from the mountains to the sea LOL).

Aragonite and calcite are BOTH calcium carbonate (CaCO3). The only difference is in the shape of the crystalline structure. Check out your beach sand using the vinegar test to see if it fizzes and gives off carbon dioxide. If it contains calcium carbonate, it should react with the weak acetic acid (vinegar) and give off carbon dioxide. If you use muriatic acid (hydrochloric acid), you should be able to get the sand (assuming it is all calcareous sand) to completely dissolve if you add just a tablespoon or two to a half cup or more of acid.

The question is, can I use this sand without any major problems if I find out its not aragonite?

You can use a lot of different kinds of sand. The question is whether the sand contains harmful impurities or not. Another question is whether it is quartz sand or calcium carbonate sand. Either will work but most people prefer calcium carbonate sand for obvious reasons.

Or could it be the crushed coral trapping nutrient even though I have lots of water flow?

Yes, one of the problems with crushed coral is that it can trap detritus. Another problem with it is that the particle size is too large and the edges are too sharp to provide the best habitat for sand dwelling critters. And still another problem is that the same volume of a finer particle size substrate will provide a far greater surface area for colonization by beneficial bacteria.

Crushed coral works best (for those who insist on using it) when it is very shallow -- approximately 1 cm deep.

P.S. -- The advantage of aragonite over calcite is that the crystalline structure of aragonite is less stable than calcite and therefore it breaks down at a higher pH than calcite. Both will break down if the pH is low enough.

The topic of the chemical processes that take place in a deep sand bed composed of fine particle aragonite sand has become rather divisive in the hobby. The claimed buffering benefits may be overstated according to some experts. I still prefer aragonite sand over any other options but I prefer to avoid discussions of the buffering capabilities.

[s1214215]

I think my problem is that my crushed coral is maybe a little deep and I ant get at it at the back corners of the tank. I think thats my nutrient sink somehow.

How deep should I go with oolitic sand in a 120cm long x 45cm wide x 60cm high tank? I will keep my DSB in the refugium, so I dont think theres so much need for it in the main tank which is too shallow I think. What do you think.

I guess I dont have a lot of choice in sand here, so will use this sand. I just hope it is aragonite LOL... Will test to see

[Rhodophyta]

Originally Posted by s1214215

....

I have no idea if the sand in my DSB is calcite or Aragonite - will check with vinegar to see (just discovered this test)....

The vinegar test is used in high school science classes on freshly fractured rock surfaces to distinguish two identical looking forms of calcite and quartz. Most of these kinds of rocks can be distiguished visually. It is just the lookalike forms that need the test. It is not useful to aquarists. It's not that useful to anyone else either, but it does fit well in the typical budget of public schools.

I don't think the sand bed or its depth in itself would be the problem, but something could be in it. A friend was setting up a marine tank. After a delay he finished the job and had a mysteriously high ammonia reading that just would not go down. He was mystified. His son said, "Dad, you know a lot more about marine tanks than I do, but I think the problem could be from those three months when the tank was empty except for the sand bed and our cats were using it as a litter box."

[s1214215]

mysteriously high ammonia reading that just would not go down. He was mystified. His son said, "Dad, you know a lot more about marine tanks than I do, but I think the problem could be from those three months when the tank was empty except for the sand bed and our cats were using it as a litter box."[/quote]

Yes that could be a reason and a big problem....

The reason I ask about the depth of the sand bed is I seem to remember reading somewhere that in shallow sand beds, if the sand is too deep, and yet not deep enough to cultivate anaerobic conditions, you end up with a nutrient sink. Which is what I think I have now with my crushed coral bed and wish to avoid when I move house and set the tank up again. So thats why I ask for opinions of how deep tp make it.. I am guessing 2 inch should be fine... What say you reeferlanders...?

As for calcite vs aragonite... I have the choice of one oolitic sand only in Bangkok and I just wondered if theres any major drawbacks to using calcite if thats what this turns out to be. I have used this in my refugiums dsb and with little bad effect other than some cyano-bacteria which I am not sure is its fault...

[Ninong]

Either aragonite or calcite sand would be fine. Aragonite would be better and it is likely that your sand is aragonite.

IMO a 3" depth would be preferable to a 2" depth.