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FAQs on Marine Alkalinity Importance

Related Articles: pH, Alkalinity, Marine Alkalinity, Understanding Calcium & Alkalinity,

Related FAQs: Marine Alkalinity 1, Marine Alkalinity 2, Marine Alkalinity 3, Marine Alkalinity 4, Marine Alkalinity 5, Calcium and Alkalinity, Phosphate & FAQs on Alkalinity: The Science of Alkalinity, Measure, Sources, Use of Additives/BuffersTroubleshooting/Fixing, Products by Name & FAQs on pH: Importance, Science, pH Measure/Test Gear, pH Controllers & pH Buffers/Buffering, pH Anomalies (Troubleshooting/Fixing), & pH Products by Name, Manufacturer,

Ideally you want "high" (but not too high) alkalinity, pH, AND biomineral content... all change with time, exposure with life processes.

W/o sufficient, semi-stable  alkalinity... algal, maintenance and metabolic problems. Lack of growth, vitality.

dKH. Not too high     2/22/14
Hi Bob,
I run a fish only marine tank and have read numerous times that the ideal value for dKH is 8-12.
I tested my local seawater, which is tropical Indian Ocean dry season and it was 7 which is meant to be normal for the tropics.
<This is so>
As we increase bioloads running tanks people talk about always having a higher value, 8-12
I can see the logic in this to try and stabilise pH by having a slightly higher dKH than normal seawater.
What I can't seem to find is any information on too high dKH except perhaps cloudiness as the carbonate precipitates.
<Many downsides in having too much alkalinity... including precipitating out alkaline earths... Interference with metabolism of most all types of livestock>
You probably guess my dKH is high, around 14. What happens if it goes higher say 20?
<All your livestock would be dead in short order>
Would the marine life die or would the water just become cloudy, I see many people worrying online about too high dKH at around the same value as mine but my tank is very healthy, there again it is fish but delicate ones at that mostly.
Kind regards,
<Cheers, B> 

Side effects of High alkalinity Hi,<Hello Kurt> I have a question.  What are the consequences of high alkalinity? I just changed my water 2 weeks ago and I guess I got a bad batch of salt.  My alkalinity is well over 20dKH (past the limits of the test kit).<Have you been checking dKH weekly and this just happened?>  No other parameters changed, as a result of the water change, just the alkalinity, and the nitrates decreased of course.  Two of my snails died and my cleaner shrimp (of 8 months) died.  Does the alkalinity affect elements that are needed for a crustacean to molt? <In a way, yes.  High dKH precipitates calcium, one of the elements needed to harden the new "skin" along with iodine, but the calcium level would have to be drastically low.> He died about 3 days after a molt.<It is possible that a fish may have hit on him.  Shrimps have a very soft shell for about 24 hours after molt and are vulnerable to attack at this time.>  I know that shrimps are usually very sensitive after a molt.  I just seems weird that he died after 8 months of being fine.  I thought the alkalinity might be the culprit.   Amm 0, nitrite 0, nitrate 5, ph 8.3, temp. 77 <Kurt, the high dKH didn't kill the shrimp.  Either it died from old age or something else got to him. I have just experienced a high dKH in my system and this certainly didn't lead to any problems.  I do have a cleaner shrimp in the tank. Sorry to hear.  James (Salty Dog)> <<Umm, high alkalinity and sudden changes therein CAN indeed kill all invertebrates. RMF>> Thanks Kurt

Calcium/Buffer Question Hi, Last week I purchased some live rock for my 55 gallon aquarium. Throughout the week the rock started to lose its bright pink color and now it is white. <Could be several things; rough shipping or curing, inadequate lighting, calcium or alkalinity, etc.> I was running copper in my tank until last weekend when I added a PolyFilter. <The copper could very well do it.> The fish store recommended adding B-Ionic calcium/buffer two part system. They said this will bring back the color on the live rock. Is there any adverse effects of adding this to my aquarium? <No. You should be doing something to maintain calcium and alkalinity levels; two part additives, Kalkwasser, calcium reactor, or even very frequent water changes. Do be sure to get calcium and alkalinity test kits so you know what you levels are and how much to add to maintain the proper targets.> Thank you, JPK <You are welcome. -Steven Pro>

Newbie <<Hello, JasonC here...>> I have learned a lot from reading all your info you are a great source of help. well now to my question I have all normal levels I bought the test kits like you recommended. The concern I have like most, is my alk. level. Its 40 ppm and the more I try to get it higher the more I raise my ph I have been using Kalkwasser for my top off water should I use baking soda with that to help my problem? <<I would put the question to you, what are you keeping that requires higher alkalinity? Unless you are keeping stony corals or clams, you really don't need to be super-concerned with alkalinity. Kalkwasser will not raise your alkalinity, but it will raise your pH as evidenced by that 8.8, which is rather high for a saltwater system. I would stop the Kalkwasser for a little while and just let the system run on its own for a while. Then, if you are still trying to bring up the alkalinity, use baking soda or a commercial buffer.>> thanks. ph=8.8 sg=.023 calcium=? alk=40 ppm <<Cheers, J -- >>

Alkalinity & Calcium Hello Mr. Fenner, <Steven Pro, part of the www.WetWebMedia.com crew, in tonight.> I love this hobby and your website makes this hobby much more enjoyable. Thank you. I have a quick question about alkalinity and calcium. I have a 55 gallon tank that has been setup for 3 months with live rock and sand. Light parameters are 1-55 watt actinic and 1-55 watt daylight. I have only a small Yellow Tang and some clean-up critters in the aquarium right now. I have been dosing with B-Ionic A&B for one month and my readings with Salifert test kits are as follows: Alkalinity 9.8 and Calcium 390 and PH 8.3. Are these numbers respectable for growing pink coralline algae? <Yes, none are pushing the upper limits, but consistent ok numbers are better than fluctuating but higher numbers.> Also, when I add a capful of Part A (alkalinity) in the morning, it precipitates out (small snowstorm). <Probably not really a snow storm. I have used this product and have just seen a little cloudiness, not a true precipitation event.> However, adding two capfuls of calcium does not precipitate out. Do I need to elevate my alkalinity and if so, how do I go about in accomplishing it? Thank you for your help and your valuable time. Dave <You are doing just fine. Have a nice and relaxing weekend watching your tank. -Steven Pro>

Carbonate Hardness Hi, Bob and experts, <greetings and salutations> I brought a sera dKH test kit for my saltwater and the test result is 12 dKH.  <excellent> Q1) Is that too high ? <nope... 8-12 dKH is a nice range. Resist going higher unless you are a coral farmer/specializing in scleractinians farmed intensively. Even then not necessary> Q2) What causes dKH to turn high ? <excess carbonates (buffer or calcium reactor)> Q3) If dKH is high, is it good ? <low and stable is better than high and erratic> Q4) What are purpose of testing carbonate hardness ? <it is an indication of stability in the system and is a critical measure to keep stable for good health and growth of many marine animals. Do test regularly and dose to keep stable> Thanks, Danny <best regards, Anthony>

Reef tank frustration (alkalinity, env. disease, invert.s...) Dear Bob, <cheers, love... Anthony Calfo in your service> I hope you can help me with this one. Actually I'm embarrassed to even be asking for help as I am by trade a professional aquarist, working for an aquarium service company for over 15 years, with 4 years prior experience in general fishkeeping before that.  <no worries at all... impossible to be an expert on all things. And a pleasure to learn a lifetime long> I was there at the inception of the reef keeping hobby!!!! So here it goes, and please don't tell anyone. <nobody but the thousands of daily FAQ readers> I have a 35 gallon reef tank with live sand and live rock. It has 2 internal powerheads with connecting sponge filters, and the back filter is an Aquaclear 500 that has a sponge and carbon. I do 15% water changes weekly, sometimes more recently because of my problems. My water chemistry is as follows: pH 8.3 Temp 76F Salinity 1.021 kH 20 and Nitrate 10 ppm. I have 0 Nitrites and 0 Phosphates. I know the kH is a little high, which has just happened recently to add to my problems.  <your dKH is actually sky high and endangers your system for a precipitous fallout. Please do water changes until you get closer to 11-12 dKH> And the problem is, any invertebrate I put into the tank seems to go into a coma. They don't die they just act like they are drugged or something, and a leg of my serpent star fell off. It's insane!!! I deal with reef tanks all the time and have never run across this.  <just curious... have you tested your magnesium or manganese levels or used Crystal Sea salt mix?> I have 2 fish, 1 Royal Gramma and 1 Yellow tail blue devil both of which are very happy and healthy.  <indeed.. all different tolerances than inverts. Still... do consider using a PolyFilter to check for color change and indication of a contaminant> I checked for copper also which only had very slight traces, probably coming from the pipes in the house.  <strange... should be zero. Definitely consider regular use of PolyFilters in the system> I have even gone so far a to have a $160.00 water test done on my water which comes from a deep well. That tested out good except for higher than normal levels of Manganese, which they said was not harmful. But could this be poisoning my inverts?  <Bingo!... they were wrong and you win the hairy Kewpie doll that bares an unsettling resemblance to Danny DeVito> After I put the crabs, starfish or snails in the tank they seem to be ok for several hours until they just slow down and stop moving. Their not dead just not moving, however some do die. I am totally frustrated and emotionally upset, I love these animals and take pride in my good husbandry.  <understood and agreed, my dear> Something is eluding me, even my boss can't figure it out. I hope you have some ideas. Any help will be greatly appreciated !!! Sincerely, Deborah  <indeed...such invertebrates have great sensitivity to metals of all kinds where fish are more tolerant. The Polyfilters are great for absorbing metals. Do consider pretreating water to screen it. Best regards, Anthony> Cheney Wells, Maine

High Alkalinity Hi Bob, I have been measuring my alkalinity/dKH with a Salifert test and getting very high numbers - alkalinity consistently around 4.5 meq/L and dKH 12.4 - 12.8. Everything I've been able to read only addresses low numbers and recommend dKH between 8 and 10. Is this dangerously high or does it just mean my PH will be that much more stable?  <Not dangerous... actually of benefit in a few ways... including pH stability> How can I lower it? Do I want to? <Stop adding buffers, biomineral supplements would be best... increase CO2 input (if you have such), just let time go by and the reductive events in your system (all captive systems) will bring it down... I would do the latter. Not to worry> I have a four month old 60 gallon tank with 45 lbs live rock 20 lbs live sand, skimmer, temp 78F, Nitrate 10 ppm, PH 8.3, Salinity 1.0225, Calcium 450 ppm. I add Calcium, Iodine, Strontium & Molybdenum once a week. My LFS didn't seem familiar with this situation and said not to worry about it, it will come down in time.  <Good idea, best> They also recommend changing 25 gallons/month which I think is high by anyone's standards (except those selling water =:o) I'm currently changing 10 gallons a month. <I'd change five or so every two weeks... and do look into buying your own reverse osmosis device for home and pet-fish use> Thank you, Brian Battles <You're welcome my friend. Bob Fenner>

Alkalinity Dear Bob, Right now I'm in California but I grew up in Rhode Island and I'm proud to know you're from my home state! <A fine place... now suburb of NY I'm given to understand...> We just introduced 3 hermits and 5 damsels to our 125 gallon aquarium yesterday. The hermits only move intermittently and got active during feeding the fish. We're worried that they're not constantly moving but only move intermittently. One just ran across the tank. At one point last night that same guy was upside down for a while. Is this normal for them? <No... not normal... do have periods of inactivity (not collective), but pretty much out "picking" at material all day long...> Could this be abnormal behavior related to our alkalinity level? A few of them are hanging out near the bubble wand. We use Coralife salt mix and our PH has been consistently 8.1. Alkalinity is 2. Tullock said that low alkalinity makes creatures have trouble with respiration.  <Yes, this is so... and very likely a contributing cause here> Do you think we should add bicarbonate or should we just sit tight?  <I would add a mix of carbonates, bicarbonates (and a little borate for good measure) here... pre-mixed in some of your system water... slowly... unless you feel very comfortable with "making your own", do use some "store bought" alkalinity/buffer here...> We have brown algae (diatoms) and green algae. This is a relatively new tank since our nitrite spike went down to zero a week or two ago. The damsels are very happy and eating heartily. <Likely the "cycling" process "used up" a good deal of your waters alkaline reserve...> Our filtration is a trickle with carbon and mechanical canisters. <Trickle/wet-dry filters are also notorious for this action...> Thanks, Allyson <Be chatting, Bob Fenner, who suggests you read over the alkalinity, pH and biomineral sections and FAQs (if you have time) posted on the site: www.WetWebMedia.com>

Alkalinity Bob, A few weeks ago you had been helping me with an office tank (75gal reef w/~65 lbs live rock) that had an outbreak of ich. (again, thank you for your help!!!) I had lowered spg to about 1.017 and raised temp to about 84 while treating the fish in a separate tank. I have since replaced the fish and brought the spg up to 1.022 and temp to 80 about 2 weeks ago. <Ah, good> Since removing and then replacing the fish everything seems fine, except a small bubble tip anemone that doesn't seem to want to open up quite all the way despite a maroon clowns constant attempts to open him up!) I attribute this to two things, first I upgraded lights from 80 watts of normal fluorescent to 260 watts of pc lighting (1/2 actinic 1/2 daylight) I cycled the lights, gradually increasing the time they were on and now the actinics run about 14 hours and the daylights 12. Could the anemone still be getting used to the stronger lighting?? The new lighting has been in place for about 3 weeks. <Yes... give this animal time... you do feed it I assume.> My second question is that since bringing the spg back up to normal, I have only been able to record an alkalinity reading of 2.5 milli/eq/litre. This tank averaged 3.2 before I removed the fish and treated the main tank for ich with the environmental manipulation. Could the low alk be affecting the anemone??  <Yes> I have a couple of derasa clams that are fine and all corals are fine. Calcium is about 400ppm and Ph is steady at 8.3. I have been doing a weekly 10 gal water change instead of every two weeks, but have only been able to get the Alk from 2.0 to the 2.5 reading I have now. I also have a money plant (Halimeda sp.) that is turning pale green to white, I assume from the low alkalinity. <Again, yes> My question is should simple baking soda restore the Alk to where it was before the lowering of spg? (prepared in purified freshwater and slowly added)  <Worth trying, yes> I also have some Red Sea brand ph buffer that I have not tried yet. Would I be ok in just adding it as per the mfg. instructions instead of the baking soda? <Yes... it is principally sodium bicarbonate...> (It claims that 100ml will raise alk of 40 gallons from 1.7 to 2.2) I only add calcium with trace elements on the weeks that I don't do water changes since I use a reef blend salt that has the calcium and trace elements in it, and I am very conservative in my additives.  <This is wise and smart> Once I re-establish a high alk should it stay high?  <Hmm, no... there is a net loss in captive systems due to driven biomineralization... in your case by clams, other life... as well as reductive events (acidifying influences) that nick down pH and alkaline reserve> In the first 4 months of the tank I never read an alk below 3.0. Finally, how much of a change in Alk is too much to quick? <A few tenths of milliequivalents per liter a day is fine> Your help once again is greatly appreciated!! Kris, PA <You're welcome my friend. Bob Fenner>

Alkalinity, KH, etc., etc. Good day. I have been drawing upon your expertise lately, and am eternally grateful for your help. Without going through all of the particulars (again!?!) I have been having a water quality issue. I have a huge diatom bloom that is not only unsightly, but is driving be loony. <This does happen... the diatoms, lunacy...> Lately, it has been so bad that the water is clouding up, and you can't even see the back wall of the aquarium when looking in the front. I don't have all of the essential test kits (yet) so a trip to the local fish store was in order. After the test, I was informed that while nearly every water parameter was perfect (reasonably), my KH (alkalinity?) was too low. It was in the 6dKH range and he informed me that it should be more like 14 dKH. Would this cause my algae bloom, and resultant cloudiness??  <Would possibly contribute to it yes... higher alkalinity would favor other (perhaps less loathsome) algal types> The proposed resolution is to add a buffer/alkalinity supplement (Kent SuperBuffer), and protein skimmer.  <Oh! The protein skimmer will REALLY help> I purchased the CPR BakPak II and set it up last night. I also added a small mechanical filter to one of the powerheads. This morning the tank was crystal clear, and I had a nice soup of skimmate in the BakPak. Looks kinda like cream of broccoli soup, w/o the cream or broccoli. Yuk!  <Don't drink it! For sure.> The last question is, should I remove the bio bale material in the BakPak?  <Good point, question... we remove it from these ourselves... so, yes> I have a 3 1/2" DSB, and 50lbs LR. Since my NO3 level is at or near 0ppm I don't want to start up a NO3 factory. I noticed that there is a difference between the BakPak II and the BakPak IIR. This is namely a lack of bio bale, and the output tube looks different. Any info is appreciated. <Please write the fine folks at CPR (cprusa.com) re this...> From the guy who says..."Why-come the ocean makes it look so easy?" <Because it is? Bob Fenner> Jason

Alkalinity and Sand Stirrers Good day Mr. Fenner... Thank you for all of your help in the past. Recently I discovered a problem with low alkalinity in my 48 gallon reef aquarium. I have also been having a huge problem with nuisance algae (diatoms, hair, bubble). Since, I added the CPR BakPak II (w/o bio-bale) I have noticed a huge improvement in water clarity, and it seems that the algae bloom has slowed considerably. Regarding the Alkalinity issue, I was getting a reading of 6dKH but after a 15 gallon water change, and one dose of buffer/alkalinity supplement (Kent SuperBuffer) my Alkalinity is reading 13dKH. Is it possible/likely/safe for such a drastic change in alkalinity?  <Hmm, possible... not likely with "one dose"... and not safe for many true/stony corals> My inhabitants seem fine, actually my hairy mushrooms are standing and swelling more than ever. <Ah, good> On a slightly different note, I've got a 3 1/2" bed of live sand that is still getting a coat of diatoms, and what I suspect may be a form of blue/green algae, or possibly cyanoBACTERIA. <These titles are used interchangeably... same organisms> It's not red/purple so I'm leaning toward BGA. Not very attractive, and my clean-up crew isn't getting paid this month (the blue hermits take their pay in astrea snail flesh, not cool!). <no> I've been considering some form of sand stirrer but am having trouble weighing the options. I get the feeling that you don't recommend the brittle stars, horseshoes, sand sifting stars,  <Some of the first are okay, and the latter in the form of Archaster is excellent><<Mmm, not such the opinion nowadays. RMF>> and you don't seem too hot on cucumbers (not the salad variety). I think bullet gobies or sleepers may be a possibility but they are quite hard to locate in my vicinity. Do you agree with these choices, or are there any other suggestions as to how to stir the sand and not allow the algae to sit?  <There are a few other choices... but these will do> I've been concerned that the sand stirrers would deplete my DSB of beneficial critters.  <This won't happen> So far my NO3 readings have been undetectable so the NNR, and conservative feeding schedule seems to be working. I appreciate your candid advice. Jason...the guy who says "My head hurts and my hands are hands are prunish but my mushrooms are lookin' better each day" <You're doing fine my friend. Bob Fenner>

High dKH levels Hi Bob, Rick your reefing friend here again. If you'll remember, I wrote to you last week about a very high dKH level in my 180 gallon tank. I have just added a calcium reactor 2 1/2 weeks ago. My readings are. Ammonia, Nitrite, Nitrate all 0. (I have 200 lbs live rock). Calcium 350, Mag. 1300, Strontium 10, Alk 24 dKH. Temp 79-80, S.G. 1.025. You suggested boosting the co2 so I went from a effluent ph of 6.5 to 6.2 and left the flow at a steady broken stream. I am using Salifert test kits. It seems that my dKH is going the wrong way. My calcium in the last two weeks has gone from 120 to 350 but my hardness has gone through the roof. You mentioned that this excessive hardness can be a problem, in what way?  <Precipitation of biominerals... direct malinfluences on livestock... Do consider trying another source of carbonaceous material to melt down, returning the effluent pH to something nearer the mid to upper 6's> I use Kent Magnesium, Molybdenum & Strontium & Tech I Iodine additives on a weekly basis. <In addition to the reactor? I would drop these for now> What should I try next to lower the dKH or should I just continue to let things run as is. <Look for a "softer" smaller granule size feeder stock> As always, your advice and guidance are priceless. Happy Birthday and good luck with the move. <Thank you my friend. Bob Fenner> Rick

Alkalinity Question Bob, All my tank readings (Nitrates = 0.0, pH = 8.2, Calcium = 420, SG = 1.024, etc.) are fine but my alkalinity is only about 1.4 - 1.5 milliequivalents per liter. This low alkalinity, I suspect is the cause of my red coralline algae bleaching to some extent. <Yes, definitely> Plus I'm worried about the few small corals I've added to the tank (Star Polyp, Mushroom, etc.). I know that eventually I need to get a calcium reactor <Not necessarily... what is the cause of the low alkalinity? Use of Kalkwasser? No soluble substrate? Too many biomineralizing organisms present with boosted lighting?...> but between the cost and the fact that a 90 gallon tank only has so much room left in the stand, I've decided that after reading you're website, I may be able to get the Alk. up into the desired range by adding simple Baking Soda. My question (finally!) is how do I add the stuff. I know I should mix it in water, but how much should I add at one time, and how frequently should I add the mix??  <About a teaspoon per actual twenty gallons of water, dissolved in system water as you state... measure alkalinity next day...> I appreciate your help (again) and I look forward to meeting you at one of the future San Diego Marine Aquarium Society meetings. Phil in San Diego <Yes. The twelve hundred gallon system meeting residence this week was very nice. Bob Fenner>

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