Duvida magnésio

[fabio simoes]

Olá amigos,

gostaria de saber da importância de se adquirir um teste de magnésio e como o pessoal faz a suplementação de magnésio do reef, e se esta suplementação é necessária, como a de cálcio.

é indicado usar mídia de magnésio dentro do reator de calcio, para suprí-lo constantemente?

o que acham dessa mídia de magnésio da nutratec e outras:

http://www.aquafishersp.com.br/categori ... oria=92844

obrigado

[Celso Suguimoto]

Eu tenho o teste da Salifert, mas desencanei com a reposicao de Mg.

Essas midias de Magnesio sao um tipo de dolomita, o Randy diz ser insuficiente

It has been suggested that adding dolomite to CaCO3/CO2 reactors can help with magnesium problems. Dolomite is a material that contains both magnesium and calcium carbonate. If dolomite is being added to the reactor to maintain existing appropriate magnesium levels against the continual depletion via calcification (for example, if the calcium carbonate being used is too low in magnesium to maintain adequate magnesium) then this is a fine approach.

However, this method is unsuitable if the goal is to raise magnesium levels. The problem is that for every magnesium ion released from the dolomite, 2 units of alkalinity are also released:

MgCO3 Mg++ + CO3--

Consequently, if one wants to raise magnesium by 100 ppm, the alkalinity will necessarily rise by 8.2 meq/L (23 dKH). The only way around this problem is to add a mineral acid (not vinegar) to the aquarium to reduce the alkalinity, and that may be more problematic than just adding magnesium in the first place.

http://www.advancedaquarist.com/issues/oct2003/chem.htm

http://www.reefkeeping.com/issues/2006-07/rhf/index.php

O uso trocas parciais é a forma mais equilibrada de se repor ions e exportar excedentes. Entretanto existem alguns elementos cuja reposição via troca de água é ineficiente como o Calcio

Necessary Supplements in Nearly All Reef Aquaria

-Calcium
-Alkalinity

Useful Supplements in Many Reef Aquaria

-Magnesium (if not maintained by calcium addition methods and water changes)
-Iron (for aquaria growing macroalgae)
-Silicate (for aquaria with sponges, snails, etc.)

Possibly Useful Supplements in Reef Aquaria

-Certain amino acids (e.g., aspartic acid)
- Fatty acid supplements


Generally Unnecessary or Undesirable Supplements in Most Reef Aquaria

-Iodine
-Strontium
-Borate
-Trace element mixture

Se os niveis de magnesio estiverem baixos tanto a RA qto CA precipitam.

Corais e as algas calcáreas do aquario podem consumir magnesio incorporando a seus esqueletos... no lugar do calcio. O magnésio é muito importante na fotossíntese

More interestingly, the magnesium levels were found to have a very large impact on the rate of precipitation. In batches with no magnesium, and at natural calcium and elevated carbonate levels, calcium carbonate was found to precipitate in minutes. With a natural seawater level of magnesium added to that mix, the precipitation was delayed to 13 to 20 hours. With double the natural magnesium concentration, the precipitation was delayed to 22 to 29 hours.

Even more strikingly, at a lower level of carbonate (closer to that of natural seawater and probably similar to that in many reef aquaria), precipitation was delayed from a few minutes in the absence of magnesium to 750 hours in the presence of natural levels of magnesium. Consequently, magnesium has a big impact on the rate of precipitation of calcium carbonate (a fact that has been confirmed by many researchers).

Magnesium is an important ion for reef aquarists. In addition to its many biological functions, it serves to prevent the excessive precipitation of calcium carbonate from both seawater and aquarium water. Since both calcium and alkalinity are very important to organisms that we keep, making sure that they are not lost to excessive precipitation is an important part of aquarium husbandry.

http://www.advancedaquarist.com/issues/oct2003/chem.htm

A presença do magnesio retarda a precipitação .... Por que isso ocorre ??

1) O magnesio interage com ions de carbonato e diminui sua concetração livre, reduzindo assim a possibilidade de precipitação que resulta em superficies de carbonato de calcio
2) O magnesio entra na superficie do cristal, impedindo de precipitar mais carbonato de calcio.

Ambos prorcessos inibem a precipitação do carbonato de calcio, sendo que o primeiro chega a aumenta a solubilidade e o segundo não.

Lembrando que a solubilidade do calcio em água do mar é 26 vezes maior do que em água doce a mesma temperatura e o magnesio é um dos principais motivos para tal.

Em outras palavras... se o magnesio estiver baixo a RA e CA tendem a se precipitar