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I Need Some Help, I Am Just Learning Of The Importance Of Alkalinity In My Reef Tank. I Ahve A 220 Gal Tank That Has Been Up & Running Well ( Other Than The Brown Algae In The Substrate That I Cant Seem To Get A Handle On) For About 18/mos. My Question Is What When And How Do I Buffer My Water? I Use Ro Water For Water Changes And Top Off-should I Be Buffering The Water Change Water And The Top-off Water Before Adding It To Tank. I Do Not Have A Top On My Tank So I Have Quite A Bit Of Evap And I Do About A 10% Water Change Every 10 Days. My Ph Seems Ok, Maybe A Little Low But Still Good 8.1 Or So. Ive Been Using Kent Marine Pro Buffer Dkh, It Seems To Be Working Slowly But Being The Lazy Man That I Am Is There An Easy Way To Maintain The Proper Alk Without Having To Test,test Again And Again And Again. Maybe Via Top-off Water And Or Water Changes Any Advice Would Be Greatly Apprteciated Thanks, Dk
 

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salthead said:
I Need Some Help, I Am Just Learning Of The Importance Of Alkalinity In My Reef Tank.... ...Is There An Easy Way To Maintain The Proper Alk Without Having To Test,test Again And Again And Again???
The short answer is "NO..."

Any time you add any inputs to your closed system, you only need to add what is being removed. Monitoring alkalinity is quite important, especially if you are;
  • adding only buffer
  • do not have a large population of hermatypic corals
  • monitoring alkalinity based on pH
  • not adding Calcium (OK, sort of a repeat of the first bullet)
  • depending on the alkalinity to control the algae in the substrate

If you do not have a large number of stony hermatypic corals using up your alkalinity, then there really is no reason to use tons of alkalinity alone as opposed to using a balanced additive, the increased levels of alkalinity as HCO3- ion will precipitate a good bit of ionic Ca++ in your water column as CaCO3. In addition, if there is a source of protons in your water column, the buffering effect of the bicarbonate ion will act to release CO2 into the water column, driving pH down and providing a good source of dissolved carbon dioxide for your nuisance algae to use for photosynthesis.

LOW or HIGH pH is not an indication of inadequate or excessive buffer, and the addition of buffer will not necessarily bring a pH much higher or lower than 8.2 in seawater. pH is NOT a measure of the alkalinity of a water column, it is an indication of the pCO2 of the water column, and although these factors are all interrelated, pH is driven in seawater by the concentration of CO2, NOT ALKALINITY. The alkalinity of a solution is a measure of how much base is present that will neutralize a quantity of acid when added to the solution. The pH of that solution is determined by the amount of acid present, and may be "buffered" so that the pH will remain at a given point as determined by the ability of the buffer to resist changes from its buffer point. Buffers, by definition, have the ability to both absorb protons (hydrogen ions) and donate protons, and by doing this, prevent large swings in the pH of such a solution. For bicarbonate/carbonate systems, in the presence of conservative ionic solutions of seawater at 80F, the pH will be around 8.2, but may be skewed depending on the atmospheric concentration of CO2 directly above the water column, and the effects of other underlying factors that allow for either increased or decreased mixing/interchange of surface water and the atmospheric CO2. The addition of varying amounts of Sodium CARbonate (not BICARBonate) to buffer builders will drive pH up depending on the proportion of sodium carbonate to bicarbonate. However, once the solution reaches equilibrium with atmospheric CO2 and the proportions of bicarbonate to carbonate, the pH of the solution will gravitate back to 8.2.

Ideally, every time you add bicarbonate (buffer) to your system, you must add Calcium as well to preserve the proportionality of the two. Corals use bicarbonate and calcium to make their skeletons (search the archives for threads on calcification and skeletalization) in a fixed ratio, and although there is some small loss of buffer to the neutralization of organic acids, this will be small in systems with good husbandry. Many ways to do this, the use of two-part ca/buffer additives like Bionic are a choice, but even better would be Kalkwasser as a replacement for your evaporative losses. This is a saturated solution of Calcium Hydroxide, and uses atmospheric carbon dioxide (as it dissolves in the water column) as the source of inorganic carbon to make bicarbonate ions (search the archives for Kalkwasser and how it works). It has the ideal ratio of bicarb to Calcium for corals to use as their source of these ions for skeletalization and calcification. Even octocorals use some of these substances, and clams as well, along with snails and crustaceans, although not nearly at the rate that hermatypic stony corals do. If you have only softies or a few crustaceans and snails, then you will only need to occasionally supplement with one of the two part additives, but with stony corals, Kalk at a minimum, and if your population of stony corals is dense, then think in terms of a Ca reactor that uses aragonite for the CaCO3 source and dissolves the aragonite with CO2 (search the archives for this information). Base your amounts of supplementation on weekly testing of your water column for both alkalinity and calcium levels. pH is not an indicator of correct alkalinity, and will fluctuate on a daily basis from a morning low of 8.0 in a closed system to an evening high of 8.4 to 8.5 in response to the level of CO2 in the water column. As the photoperiod starts, photosynthetic machinery in the autotrophs of the system will begin to remove CO2 from the water column and consequently increase pH until the high of the day at the end of the photoperiod, then as the light go out, metabolism shifts from primary production to respiratory CHO catabolism, and CO2 levels begin to rise. This rise in CO2 levels then drops pH back down to the morning low, when Photosynthesis again starts up with the increasing light levels and the cycle starts again.

Many different means of maintaining appropriate alkalinity and Calcium levels, but keep in mind that they are both needed for reef aquaria, not just one or the other.

HTH
 

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aDdendum to the above: If you add kalk so that it is delivered at the intake for the skimmer, it will help export some of the dissolved inorganic phosphate from the water column. Biggest problem with this is that not much of the phosphate will be available as free phosphate for this removal process, but it will be part of a multipronged attack on phosphates (which are the trigger for your algal bloom that you're experiencing.) Many other means of reducing phosphate both before and after it is available to your water column, best to remove phosphate sources before they become available to the water column (and Will be absorbed by algae and bacteria of the system).
 
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