Nitrates dissolving Agaronite?


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Yesterday I got into a discussion on Myspace with a kid from Marrietta who works at Pets Unlimited. He was in favor of the use of bioballs in a reef set-up and had this to say on Nitrates:

"actually it is recommended to have a nitrate level of 10ppm in a reef aquarium, as it helps to dissolve the aragonite so essential trace elements are released into the aquarium."

It was my understanding that a pH above 8.0 helps to dissolve aragonite, and dissolving aragonite has nothing to do with trace elements- it maintains a good buffer/Ca level.
He also had some not-so-nice things to say about the ARC, but he was young (19) and is probably hot-headed. Is there any truth to what he said or is he confused?
My understanding is the alkalanity of the water is what dissolves calcium carbonate. The more acidic the faster it dissolves. There are two articles that go way in depth on this subject and are considered the defacto standard on these issues:"></a>



There is a passage in the later article that could maybe confuse someone, but if you read it more than once or have half a brain I don't see how you would get confused.

<p style="text-align:left;"><span style="font-family: Times New Roman;"><span style="font-size: 13px;">[B]7. Use a [IMG]"><span style="color: #0000ff;">sulfur denitrator</span></a>[/B]. In these systems, bacteria use elemental sulfur and produce N2 from it and nitrate according the following equation (or something similar):</span></span>
<span style="font-family: Times New Roman;"><span style="font-size: 13px;">2 H2O + 5 S + 6 NO3- </span></span><span style="font-family: Wingdings;"><span style="font-family: Wingdings;"><span style="font-size: 13px;">à</span></span></span><span style="font-family: Times New Roman;"><span style="font-size: 13px;"> 3 N2 + 5 SO4-- + 4 H+

It has also been suggested to pass the effluent of such a reactor through a bed of aragonite to use the acid (H+) produced to dissolve the calcium carbonate, and thereby provide calcium and alkalinity to the aquarium.</span></span>
<span style="font-family: Times New Roman;"><span style="font-size: 13px;">While that is a fine idea, it doesn&#8217;t add much calcium and alkalinity to most aquaria.</span></span>
<span style="font-family: Times New Roman;"><span style="font-size: 13px;">To estimate the magnitude of the effect, we start with a liberal estimate of how much nitrate might be removed. [B]Say 10 ppm of nitrate per week.[/B]

10 ppm nitrate = 0.16 mmole/L of nitrate

Since 4 moles of H+ are produced for every 6 moles of nitrate consumed, this will produce

0.107 mmoles/L of H+ per week</span></span>

My guess he or someone else read this and derived that the 10ppm was the cause of aragonite dissolution. He is 19 so I would certainly cut him some slack, but telling people to keep nitrates high at a LFS when clearly doing so could harm there tank is pretty scary... and probably typical at least in the bad advice sense.

BTW, people here know there stuff. Not only do they keep aquariums up and have some stunning success, but they freely give advice and help a fellow out whenever needed. You can read all the books you want, but practical experience especially in the ART of reefkeeping is paramount. At 19 it is unlikely he has a lot experience in the matter... possible, but not likely.
There is indeed no interaction between nitrate (NO3-) and aragonite (typically CaCO3). Nitrate is involved in the">nitrogen cycle</a> in the tank, and plays a role in the availability of nitrogen and oxygen to creatures, but neither affects pH (concentration of H+ and OH- ions) nor affects the CaCO3 bond in any way. One of our chemistry experts will have chime in with more detail.

A pH below 8.0 (more acidic) helps to dissolve calcium; this is why people use a calcium reactor with CO2 (and keep the pH around 6.75 in the reactor).

I think the easiest way to debunk this is to point to many successful reef aquariums around the world (including our own oceans) and easily see that they all have a nitrate level far less than 10ppm - usually 2ppm at the most.

As for his comments about the ARC- for any give community of people, there will always be supporters and dissidents. The club does it's best to provide a productive, healthy environment, and every once in a while, someone will feel slighted in some way. With over 450 members, it's just bound to happen, esp. with the younger, more "revolutionary" crowd.
Thanks for helping to clear this up for me, guys! As for the club I've found this forum to be a great help and everyone has been extremely helpful and knowledeable without being condescending. Thanks for helping make it this way, and I'm looking forward to meeting everyone at Feburary's meeting!
Can't wait to meet you as well. THis is one reason having forums is so great. YOu post one thing and 15 people respond with scientific facts.
I agree! And when you're dealing with live animals I would never just take one person's word for fact. I research online & in books, but for more obscure stuff it's very nice to have the opinions of people who have actual experience!
Well there is no truth to what he said about the ARC. Im 16 and I can tell you that I have learned so much about myself and about reefing through this club. There is no book or anything anything else that is better than this sight. IMO. We get to learn by trial and error. But here we learn before we have the error because everyone shares there experiences. I used to work at a Fish store (Atlantis) and I learned alot from there in a year but I have learned much more here already. I love it!
wbholwell wrote: ...a kid from Marrietta who works at Pets Unlimited.
He also had some not-so-nice things to say about the ARC, but he was young (19) and is probably hot-headed.
I was going to leave the chemistry lesson to "the professors" (i.e. people with WAAAAY more knowledge about such things than I have), but I thought I'd throw in on this part.

Bear in mind, this is my opinion based on experience I've had at dozens of LFS over the years, both good and bad, in Atlanta, the Washington, D.C. area, and the Tampa/St. Pete area (my 3 home towns).

As a club, we have a collective of knowledge, standards, equipment, and livestock in a hobby where the LFS is used to being all that to the customer. On the knowledge, I have found ARC members (and reef community members at large) to have more correct information than some LFS staff. Not always, but often enough. I *know* we all have standards that many LFS do not appreciate when we comparison shop their livestock. We have equipment that we trade and find each other deals and best prices on. Lastly, we have a large, hopefully growing population of livestock that we trade amongst ourselves.

The first 2 tend to offend some LFS and staff. The second 2 may be seen by some as essentially taking money out of a LFS' pocket. Some natural resentment will occur and trickles down through the employees.

The reality, of course, is that the club breeds interest and capacity and provides a source for new reef keepers that might otherwise be put off by the complexity. Ultimately, the LFS market benefits.
Another good point by George. In a way we do take buisiness from them but in the end we are getting them more buisiness by recommending them to new members.
I agree that George makes a great point. To further that a bit more, LFS are setup to make money and sell you equipment and such. Here when you ask, you will get unbiased opinions in that regard. I am probably not going to tell you to buy that whizz bang $300 UV sterilizer to keep your ick out breaks under control unless that is something that I would actually do.