The Truth about Sand in a Saltwater Aquarium

Think you know all about sand for your saltwater aquarium? I thought I did, until I learned the truth about sand by listening to the ReefThreads podcast.

aquarium sand by gurdonark

Saltwater aquarium image by gurdonark

In their podcast 124, Gary and Christine (the usual hosts, if you don’t listen to the podcast) had a guest on named Boomer, who sounded like he knew everything about sand you could ever want to know…and quite frankly, he confirmed that a lot of what I thought I knew about sand was wrong. So unless you have a bare bottom reef, you’ll love this podcast. I highly recommend you download and listen to it, today.

So, if I ever gave you bad advice about sand, I apologize.

Before listening to the podcast, I had 2 pretty firm beliefs about the use of sand in a saltwater aquarium:

  • Belief # 1: Aragonite sand in a saltwater aquarium can have a beneficial effect as a buffer and calcium source.
  • Belief # 2: Sand containing silicate could be disastrous in a saltwater aquarium, because it will fuel the growth of problem algae.

Well, it turns out that both of those beliefs (which I believe to be broadly held by a lot of aquarists) are wrong.

crushed coral

Note the crushed coral in this image by smoMashup_

It turns out that aragonite sand initially DE-BUFFERS saltwater—and once it stabilizes in your saltwater aquarium, it isn’t going to do much of anything at all unless your pH drops crazy low—as in below the pH of neutral freshwater. So…eh…I humbly apologize for not know that. It kind of blows my mind. I’m positive I’ve read the OPPOSITE of that in a bunch of places. The buffering capacity of the sand is often touted as a benefit for keeping the pH of your coral aquarium stable.

As far as silica-containing sand…Boomer said that the glass that your aquarium is made from is going to dissolve faster than the silica (he also called it quartz) in the sand…so essentially, that whole thing about fueling problem algae (diatoms, cyano, or algae) is bogus.

From my perspective, there are 2 morals to the story:

  1. Buy whatever sand you want. Go for aesthetics—not chemistry—the sand appears to be roughly inert (at least to the extent we’re interested).
  2. Don’t believe everything you hear or read…even from guys like me. There is a lot of good information out there, and there is a lot of bad information out there. I try my best to put the good out there—but do your homework—and let me know if you find something on the site that may need some adjusting—my goal is to be a helpful source of information.

So what do you think about that? Are you as surprised as I was to have these myths debunked?

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  1. I too have read about aquarists having to top off their sand after years, who knows. I like the way you write informatively and calling on multiple sources its a fun read and you have the site arranged well I really like it. at work killing time!

  2. Author

    Brandon, thanks for the comment. I think the whole truth about sand issue points to how important it is to be clear on the facts–and to be scientific in our pursuits. It also speaks to the need to be flexible in our beliefs in the light of new information. Thanks again for the great comment. Glad I could help pass the time at work…wouldn’t be the first time I’ve done that…

  3. Al,

    I’m new to all this, was given a tank last week and both my wife and I agreed if we are going to have a tank we are going to do it properly and create the Indian Ocean in our lounge!! This was before I re;used how much I had to learn but I found your blog and have read 15-20 articles today and am loving it. Just hope the moment stays. I enjoyed this article but without dates or blog numbers it is hard to know which articles this supersedes.

    My question is does this means that ‘live sand’ is simply a gimmick/myth? We definitely want a sand layer at the bottom of our tank. Do we need to buy filtration sand or could we just use regular sand?

  4. Author

    Hi Ben,

    Thanks for being such an avid reader, and for leaving a comment/question!! I do appreciate it and hope the moment stays, too! As far as your question about live sand, it is certainly not a gimmick. It’s a genuine product that has some value and utility. I like to think of it as a reasonable benefit at a relatively high cost (at least, to me). You can realize a similar benefit, naturally, over time. If you’re trying to manage it on a budget, try to get a few small pieces of live rock, maybe a handful of live sand from a guy like me, and you ‘seed’ the tank with bacteria and sometimes invert life, much the same as you can seed sourdough yeast from sour dough. If you have time and patience on your side, your sand will indeed become its own ‘live sand’. if, you’re the type that wants it right away and can afford the price, you can buy the live sand–or you could buy 1 bag of live sand and fill the tank with other ‘regular’ sand.

    The key, if you’re buying other regular sand is to try and make sure it is prewashed and hasn’t been treated with harsh chemicals. That’s the other reason the reef sand is sometimes better–less risk of something bad getting into your tank.

    When I filled my tank, I used ‘play sand’ from a local home depot/lowes store. Make sure to rinse it extremely thoroughly first in a slop sink, sand is surprisingly dirty 🙂

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