Is dkh 8 bad to run a tank at?

[Baldwin]

Ph is stable at 8.00 and salinity .024. Calcium 450-500, nitrate and phosphate undetectable. I have b-ionic on hand and also kalkwasser. I was planning on keeping the tank at 11 dkh but the corals all seem really happy. I have mostly softies and Lps. The only thing I can notice is the softies seem to molt a lot. I know 8 dkh is close to natural conditions but most people have told me I should keep it higher. Any experts out there that can fill me in?

[andrewsky]

im no expert, but i know that dkh is suppose to be between 8-12 dkh, thats what i read up online. mines at 10 dkh and my corals are thriving. and if your using B-ionic that should help atleast raise it a little. but i'm positive your fine with 8 dkh, but it could be raised just for good purposes.

[djkms]

Anything below 9 seems to really upset my corals.

Sent from my Droid Incredible.

[flyyyguy]

8 is perfect IMO

its where all of my tanks are kept

[sland]

I try to keep mine between 8-10....8-9 being my happy place

[bertoni]

I think 8 dKH is fine for most systems. Soft corals should be okay over a fairly wide range of alkalinity levels.

[Baldwin]

So basically, I know that my system fluctuates between the monthly 25 percent water changes the levels are going to lower, but I haven't added any kalk or calcium to the tank and the levels are still good over a month since last water cahnge. What I gather from this information is that I shouldn't be adding anything to the tank in terms of alk/calcium and that just doesn't seem right does it?

[bertoni]

If the dKH stays above 7, the tank should be fine. :)

[Baldwin]

Ok good deal, i think i may still add like 20 ml of b-ionic 2 part a day maybe to stabilize the levels more?

[bertoni]

The only good way to pick a dosing level is to measure the alkalinity each day and dose enough to replace the amount consumed.

[myerss]

DKH should be 8-12, I shoot for 11. I think if you are under 8 you should try and raise it.

[bertoni]

The usual range recommended here is 7-11 dKH. 7 dKH already is a bit above natural seawater levels:

http://reefkeeping.com/issues/2005-11/rhf/index.php

[Baldwin]

Yeah I know I need to test, but I seriously doubt 20 ml a day will raise either much, so if I play it safe and just try to maintain or even slightly lower my levels between changes Im hoping I will be good.

[preef]

I used to target 11-12. I accidentally dropped it to 7 slowly (over a 4-6 wk period) and bam my corals came to life as it was dropping. I'm targeting 8-9 now. I'm getting better colors and growth at a lower alk than I did at higher levels.

[xsboost]

i used to target 11-12. I accidentally dropped it to 7 slowly (over a 4-6 wk period) and bam my corals came to life as it was dropping. I'm targeting 8-9 now. I'm getting better colors and growth at a lower alk than i did at higher levels.

+1

[Tracey2]

I find my lps are happier with a lower alk 7 but sps have better colour at 10/11.

[bertoni]

That seems to be a fairly common occurrence with some stony corals, especially when carbon is being dosed.

[Baldwin]

I am ising biopellets. Maybe thats why they look good.

[Baldwin]

I accidentaly dose 10 ml of B-ionic without diluting the bottle. Is this dangerous or can you dose smaller amounts without dilution?

[bertoni]

It's the same as dosing the equivalent amount of diluted additive, as long as you don't see any permanent precipitation at the time of dosing. I wouldn't worry very much.

[Baldwin]

I dont see any bad effects, but I went ahead and diluted the rest just to be safe.

[Flems]

I used to target 11-12. I accidentally dropped it to 7 slowly (over a 4-6 wk period) and bam my corals came to life as it was dropping. I'm targeting 8-9 now. I'm getting better colors and growth at a lower alk than I did at higher levels.

Same here. I used to target the 10-11 range.

Ive since lowered it down to 7.5-8.5 and the growth and colours (in both SPS/LPS) I have now are quite better than before. The growth was the largest change.

[chris88]

10-12 is way to high in my opinion. 7-9dkh is ideal anything higher then this is way to much above natural sea water and can cause burnt tips when carbon doing and other problems.

[fcmatt]

i used to run high but now i am around 7-8. the mostly stony corals seem to enjoy it.
some corals have good color while some others do not but that is normal in most tanks.
some pieces just do not color up for everyone depending on conditions.

[zach_24_90]

anything from 8-12 if fine mine changes depending on what im keeping my Ca at

[reef_doug]

8 dKh is fine, but stability is very important with SPS. I like to tarket Ca at 420 with Alkalinity at 8 dKh.

[brianMayo84]

when is it considered a bad flucation of ALK?

[reef_doug]

when is it considered a bad flucation of ALK?

I would say 1/2 dKh, but interested in hearing from anyone that has science backing up alkalinity fluctuations in regards to stressing corals.

[HighlandReefer]

This is one scientific article I found related to the subject. FWIW other experiments have been completed as well and found the same results. No coral problems were noted when the alk levels were increased. Perhaps some of the complaints of coral tissue necrosis are related to low DOC levels in tank water due to the efforts of many hobbyists who try to maintain ULN systems. IIRC, the recommend level for coral growth is around 1 ppm TDOC, but we have no kits which can measure this much less decipher the type of DOC. Perhaps in some hobbyists' tanks the TDOC is actually high from heavy feeding and this could have adverse effects when combined with sudden alk changes. I have a lot of questions and there are a lot of variables that need to be eliminated to determine why TN occurs for some hobbyists from alk changes & not for others.

FWIW, there are 51 pages in this document & I only posted a small portion of it. ;)


ENHANCED GROWTH OF THE SCLERACTINIAN CORAL PORZTES RUS
THROUGH ELEVATED ALKALINITY
BY
Craig John Zievis
B.S. University of Maine, 2003
http://www.library.umaine.edu/theses/pdf/ZievisCJ2005.pdf


From it:

The information gained in this project has multiple practical implications. The most readily useful among these is the ability to enhance commercial coral aquaculture by supplementing seawater in aquaria containing corals with inexpensive NaHC03 to increase coral growth significantly. By so doing, culturists will be able to bring their corals to market or fragmentation size more quickly than by relying on normal seawater, the current practice. Therefore, production can be increased while scarcely increasing costs, which can translate to into increased profit potential.

Overall, my experiment showed that growth can be increased up to five times the normal rate when TA is increased 1.6-fold, while Marubini and Thake's research demonstrated that growth could be doubled by increasing the alkalinity 2-fold by adding NaHC03 to seawater. Thus, the enhancement of growth rate through NaHC03 addition likely lies between two and five times the growth rate exhibited under normal seawater carbonate parameters. Taking a conservative scenario, when growth is doubled, the amount of time required for the coral to grow to a marketable size is effectively cut in half. Thus, twice as many corals can be produced for the same allotment of space and operating costs. Therefore, as long as the market demand does not fall below the rate of production and corals are sold as they reach marketable size, the savings afforded by doubled growth would be substantial. Of course, it remains to be seen if other scleractinian corals will exhibit the same response in to elevated alkalinity as the Porites rus nubbins that were used in this project. Because the nubbins were held in small aquaria with only a bubbler for circulation and without any other reef biota, I assume that their growth rates under all conditions were reduced relative to what they would have been in a tank simulating natural conditions on the reef (which was the original intent of this project). This is important because given my results, it would take -533 days for my experimental superior nubbins to attain a size suitable for fragmentation. This is far too long for commercial production. However, in a reef tank environment with a full complement of reef organisms and strong alternating flow, I expect that the grow-out period would be considerably shorter that what was indicated this study. Preliminary experiments suggest that the diverse algal, invertebrate, and fish inhabitants of a reef tank fare well at elevated alkalinity approaching that used in my experiments, so the approach seems feasible.

In addition to the potential to enhance commercial coral aquaculture, the increased growth of corals via NaHC03 addition may help reef restoration efforts.Whereas now reefs are left to recover, more or less, without human intervention from significant disturbance events, coral collected from local reefs may be cultured ex situ and grown relatively quickly for "reseeding" heavily impacted reefs. While this method is not currently practical for reef restoration efforts, in the future we may find many species of coral in danger of extinction with the only viable method for preservation being through ex situ culture. However, it is not yet known how corals will react to being transferred from the DIC enriched water of an aquaculture facility with stable water parameters (light regimes, temperature, turbidity and flow etc.) to natural reef seawater with highly variable conditions.

I conclude that the growth of commercially marketable corals can be significantly enhanced via the addition of NaHC03 and long term exposure to unnaturally high alkalinity is not detrimental to coral health. Additionally, the retardation of coral skeleton growth caused by a lack of feeding can be, at least partially, compensated for by the increasing the DIC pool in external seawater. In this project the lack of feeding was completely compensated for by the increased external DIC pool.

[Jimmy54]

When phosphate and nitrate are undetctable, you're probably close to an ULNS.
In that case 7/7,5 dkh would be the target you are looking for.
8 is not too bad, but I would'nt run an ULN tank any higher than that.

[Jimmy54]

I conclude that the growth of commercially marketable corals can be significantly enhanced via the addition of NaHC03 and long term exposure to unnaturally high alkalinity is not detrimental to coral health.

What about the calcification process: Ca2++2HCO3 <=> CaCO3 + CO2 + H2O
That's what corals do, nothing more and nothing less.
So for each calcium ion it needs 2 bicarbonates to create one molecule CaCO3 for its skeleton.
Adding more bicarbonates will not make corals grow faster, adding enough bicarbonates compared with calcium is what they need.

[tmz]

Higher alk insures an easy reach for needed bicarbonate and encourages growth provided calcium is adequate. The extra CO3 also uses up some H .With less H in the water it's a bit easier for the coral to squeeze one out as it uses HCO3 and Ca to produce CaCO3.

[tmz]

Steady alk between 7 and 11 dkh should be fine in fed systems even with very low/undetecable nutrients,ime.

I tend to think the TOC buildup when carbon dosing ,particularly monomers including sugars are a more likely cause of trouble than alk levels provided alk is steady. Skimming and gac use help run down TOC levels.
Precipitous drops in dkh particularly below 7dkh often cause trouble.

There is a notion that corals kept without feeding in water void or nearly void of useable phosphorous and nitrogen just don't grow enough tissue to keep up with skeletal growth at higher alk levels but there is no data to support that thought. Maybe starving corals just can't spend much energy for growth .

[HighlandReefer]

Increases in the calcium concentration will also effect the growth rate of coral skeleton like increasing alk levels which has been demonstrated in research.

The CO2 concentration plays a big role as well, where increases in CO2 above natural seawater levels retard skeletal growth. Lower pH levels in tanks are a result of higher CO2 concentration. Some studies have shown that a pH level below 8.0 causes problems for coral when alk and calcium are at the same concentration as NSW.

So calcium and CO2 levels can have a profound effect on coral growth, which may play into hobbyists seeing TN in coral since hobbyists' calcium levels may be high as well as the CO2 levels. Perhaps higher calcium & alk levels may help offset higher CO2 levels. Like I said there are a large number of variables that can play into the TN seen in coral from some hobbyists and not others. An example may be if a hobbyist has an alk level around 7 dKH and also has a high CO2 level with a pH around 7.8 - 7.9, which could result in tissue necrosis, where hobbyists who have a higher alk & calcium level than normal may offset the issue of low pH.

[HighlandReefer]

This research project demonstrates the issues I have discussed in the above post:

Effect of calcium carbonate saturation state on the calcification rate of an experimental coral reef
http://imars.usf.edu/~cmoses/PDF_Library/Langdon%20et%20al%202000.pdf

[HighlandReefer]

Another factor that has not been discussed so far is hobbyists are stating their alk concentration is say 8 dKH. With the problems we have measuring alk levels using hobby grade kits, there are factors such as whether the kit is for fresh water or marine water & if the borate level is actually higher or lower than that of NSW that can have a profound impact on the actual amount of carbonate/bicarbonate used by coral (this is the level we are acutally interested in), meaning the true carbonate/bicarboante level can be off significantly over what the kit provides as a reading. In other words, one hobbyist's reading of 8 dKH and another hobbyist's reading of 8 dKH can be significantly different in reality. ;)

Based on the possible factors that can cause errors in hobbyists' alk readings, there can easily be a discrepancy of 2 dKH or so, between the given values by hobbyists & the true alk level . The resulting carbonate/bicarbonate available for coral usage is greatly inpacted by this.

[Jimmy54]

Higher alk insures an easy reach for needed bicarbonate and encourages growth provided calcium is adequate. The extra CO3 also uses up some H .With less H in the water it's a bit easier for the coral to squeeze one out as it uses HCO3 and Ca to produce CaCO3.

Less H in the water to a certain extend I guess? - less H means higher pH.
And I don't believe raising dkh with e.g. NaHCO3 from 7.5 to 8.5 or 9 will up my pH from 8.3 to 8.5.
But then again, I'm not a chemist :reading: Never to old to learn.

[HighlandReefer]

Randy demonstrates the effect of increasing alkalinity on pH for normal CO2 levels and increased CO2 levels over NSW in this graph:

Low pH: Causes and Cures
http://reefkeeping.com/issues/2004-09/rhf/index.php

From this article:

http://reefkeeping.com/issues/2004-09/rhf/images/Figure1.jpg