Marine Topic Of The Week, 04/28-05/05

[steelhealr]

There isn't much discussion on Boron, another obscure element that we see test kits for out there (Salifert). Some reefers test for it. Some even dose it. What is this cool sounding element?

Chemistry

Boron is B on the Table of the Elements and has an atomic weight of 5. In seawater, it exists as two forms, boric acid, B(OH)3 and borate B(OH)4-. These two are in equilibrium similarly to how CO2 and H20 are in equilibrium with HCO3- (bicarbonate). 70% of boron is present as boric acid

What does it do?

The presence of boric acid and borate in our seawater results in some buffering. If the pH rises in our tank, boric acid combines with a water molecule, gives off a hydrogen ion and becomes borate. The reaction is as follows:

B(OH)3 + H2O <---> B(OH)4- + H+

The relative contribution of boron to tank stability and pH buffering, without going into math, is relatively neglible. However, it is interesting to note that there are 2 artificial sea salts out there that are relatively high in supplemented boron, Seachem and Coralife. Instant Ocean was lowest:

NSW, 0.44 mM boron
Seachem 0.49 mM
Coralife 1.29 mM
IO 0.31 mM

Causes for loss of boron

1) deposition in corals
2) precipitation with calcium carbonate
3) uptake by algae

Can it be toxic?

Yes. As always, never dose your tank with what you don't test for. Marine fish are more sensitive to boron levels than freshwater fish are, in general. The marine isopod Limnoria lignorum has a 24-hour LC50 (that is, the concentration at which 50% die in 24 hours) of only 2.6 mM (28 ppm boron).

Salifert makes the only boron test kit that I am aware of and also the only additive supplement.

Most tanks are repleted with regularly weekly water changes. You can also use borax to supplement boron. 1 teaspoon in a 100 gallon tank will raise the boron level by 0.21 mM (2.3 ppm).

Final Comments

Slight depletion (or excess) of boron will go unnoticed from a pH variation perspective. Even the total absence of borate might not be detected in the magnitude of the daily pH swing present in most reef tanks. In general, I don’t think that most reef tanks are likely to suffer much if you don’t measure boron and just let the level be determined by the ebb and flow of boron from your salt mix and the various sinks in the tank. For whatever it is worth, I’ve not measured the boron level in my tank.

 

[steelhealr]

Not many boron comments...OK..topic released. SH

 

[Mr Miagi]

LOL. I read it though SH. Very good article. Maybe there should be another folder in the Fact section for these weekly discussions?

I didnt reply cause I didnt have much to add. All I can say is, dont add any additive UNLES you TEST for it. But you said that already too!

 

[steelhealr]

If William gives us a separate FAQ section, I'll gather them up and put link's there. It would be nice to have other forum members do up some brief and interesting topics. SH

 

[Matthew5664]

A 'chemistry in the aquarium' section would be very helpful (FW and SW). I've just read through about 90 pages on Phophate and its role in the ocean and life and would like somewhere I could go and pose questions?

As for Boron.....

I think some corals like it more that others and for some reefers B additives are a common thing. Just goes to show that resurch into the species you are keeping is a must!