Tank with HIGH ph

sonny

Member
I have a 240 gallon tank that has been set up for about one year. It has a strong pump (iwaki 55RLT) that pumps about 800-900 gph after the 6 foot rise. It has base rock in it (probably 300 pounds) that was dry, and is now (after a year) full of bacteria, and a Lifegard fluidized sand filter. It is a fish only tank. I post here because most reef keepers know more about water chemistry than other saltwater keepers.
Since set-up, the ph in the tank has been very high. When I first added the salt, it was almost 9.0 . It had dropped to about 8.4, after which I added some fish, but now has inched back up to stabilize at about 8.6 (it's darker than the highest reading on my test kit, which is a SeaTest brand). Since high ammonia and nitrites make the ph drop, I know that is not the problem. Ammonia and Nitrite are zero, and alkalinity is 2.5 meg/l. I haven't measured nitrate, as it is a fish only tank, and fish don't seem to mind high nitrates. I have CaribSea sand as a substrate. I don't want to add chemicals to drop the ph, but I can't think of anything else to do. I've been keeping saltwater tanks for over 20 years, but I've never had a tank that ran a High ph. Any ideas????
Sonny
 

keitho

Member
how old is the test kit? if it's old, test kits DO go bad so maybe think about replacing the one you've got. also, the alkalinity is measurement of buffering capacity, i.e. resistance to change in pH. you may try to increase the alkalinity since certain amphiprotic ionic species like bicarbonate (HCO3-) and bisulfate (HSO4-) will help to neutralize excess bases as well as acids. hope this helps.
 

sonny

Member
Thanks Keitho. The test kit has an expiration date on it (I think it's 2003). It is about 1 year old. I tested it this afternoon, and it said it was 8.2 . I did add a protein skimmer to the tank yesterday, and I wonder if that had anything to do with it? I would think the skimmer would only help raise ph, rather than lower it though, as it would raise oxygen levels and remove organics from the water. The water was noticably clearer today due to the skimmer!
Sonny
 

keitho

Member
adding a protein skimmer is a really good thing. i have a little airstone driven skimmer in my tank. you hear a lot of people talk poorly about airstone driven skimmers, but i love mine and i don't mind the periodic maintenance. i dont really know that you can "blame" the decreased pH on the skimmer, but it's really good to hear that you've gotten the problem under control. the only reason i could think of is that maybe since you're using air as the gaseous phase in the skimmer, maybe you helped balance not only oxygen but also carbon dioxide levels (which, of course, would lower pH). sorry i don't have a definitive answer, but at least your problem has subsided! hope this helps...
 

sonny

Member
I thought about adding a 2-part calcium buffer solution to the tank, but since it is fish-only (except for a few hermit crabs and some snails), I didn't think that was really needed.
My source water is tap water, but it has a ph of 7, and I have had really good results using this tap water for many years. This is actually a tank I maintain for a doctor's office. I don't think it's feasable to add a RO unit at the office where the tank is. There is not a place I could keep a reservoir of RO water, and I certainly don't want to have to transport it from home. I do have a RO/DI unit at my home, however.
The fish in the tank are doing very well. I have a maculosus angel, a twinspot wrasse, a coral beauty, and 3 yellow tangs. I hope now the ph has stabilized. I will add some buffer to try to get the alkalinity up. Thanks for your input.
Sonny
 
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