Alk drop after a water change??

cracker

Well-Known Member
So after a water change the ALK can drop almost a whole point. ( from 8.0 to 7.1 last round) . I dose it back up to 8 in less than 25 hours. I do 20 /25 gl water change . Ya think this is too much water? I have mostly LPS with a few encrusting & a Montipora for now. I recenty melted an Acro .Just trying to keep stability around .05 changes. So my main concern is will this significant drop then back to normal ,over 24 hours going to piss off sensitive corals? Thanks for any Op's !
 

DaveK

Well-Known Member
What you need to know to resolve this is the parameter for pH, calcium, and alkalinity of your tank water before the water change, the water your going to use for the water change, and of your tank water after the water change.

Once you get all that information, you should be able to see what is likely going on and work toward correcting it.

If I had to guess at this point I would suspect that the new water is much lower in alkalinity than your tank water.
 

Oxylebius

Well-Known Member
The first thing I thought Dave hit on, the new water is much lower in alk than the water in your tank. You can test the newly mixed water to determine this. If so, I suppose you can dose the new water to get the alk higher, then do a water change. Or find a new salt that has higher alk levels.

I would also test the Ca & Mg to see where those levels are in the new water to determine if they also differ from your tank water. If you are able to test pH then do that as well (pH is something I never test for).

I strive to have the tank water be at the same levels as the salt mix that I use. Every new batch of salt I test out to see what the levels are. But, I have to admit that after that I don't. Sometimes a shaking (or rolling) of the salt container helps to mix dried salt (which may have settled).

Have you changed salt mixes lately? If not, do you think the company changed their salt mix?
 

cracker

Well-Known Member
Thanks for the reply's . I use regular Red Sea for this tank. If I use it right after mixing the ALk is fine. Sometimes though I can't do it when planed & it may stay in the barrel a day of two , it will drop . As I was saying I can easily dose it up to where it needs to be. But I'm lazy ! Just wondered if this 1 point swing every couple of weeks Will tick off the corals. I'm about to try some more sps & want to do this right. Thanks ! :)
 

Pat24601

Well-Known Member
I’m less experienced than all 3 of you, but I used to have this problem and what I did is dose both calcium and alk immediately as I did each water change. After a few times testing, I knew exactly how much to do without even checking my parameters (although I did occasionally just to be sure).

That said, you have much more sensitive corals than me. I mostly had LPS, softies, and easy to keep SPS.
 

DaveK

Well-Known Member
Thanks for the reply's . I use regular Red Sea for this tank. If I use it right after mixing the ALk is fine. Sometimes though I can't do it when planed & it may stay in the barrel a day of two , it will drop . As I was saying I can easily dose it up to where it needs to be. But I'm lazy ! Just wondered if this 1 point swing every couple of weeks Will tick off the corals. I'm about to try some more sps & want to do this right. Thanks ! :)

If your seeing this occur, it could indicate that the alkalinity is being absorbed by something or that it may be getting removed by something precipitating out. Is your mixing container getting coated with anything after a couple of days?

You need to be a bit careful here. While it's easy to supplement alkalinity, you don't know what else is being affected. It can be a problem if you need to make too much of an adjustment.

Also some salts mix to fairly low alkalinity. Be careful if you switch salt brands.
 

Oxylebius

Well-Known Member
I usually store rodi water so that I can mix up on demand if I need too. I don't store mixed salt water, so not sure what else to offer, but Dave hit on what I was thinking, where did the alk go (as in who absorbed it or precipitated out)?
 

cracker

Well-Known Member
Exactly !
To Pat If You had easy SPS You are more experienced than I am !
I do get the normal buildup on the walls of my mixing barrels. I can easily assume that's where the alk is going. Next round I will purposely wait a couple days & test. Just to see It's going somewhere !
so next time ,I will test right after mixing then wait a couple days & test again. Red Sea states, (I'm reading this from a new full bag of salt) , the Alk at 77 temp will be .7.8 to 8.2. I know,what one reads & what is reality is usually two different things.
 
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cracker

Well-Known Member
I took an average of the past 7 days ( how much I dosed) came to 19.2 mls . I started dosing 20 mls regardless of the nightly tests. will do this for 7 days. If it's still low I will increase the amount. I dose 10 mls in the morn & eve. This testing & dosing nightly is crazy !
 

Oxylebius

Well-Known Member
I'm confused are you testing and dosing the tank or the storage water 2xdaily?

If storage water, then yes, crazy. Something that may help the storage water, if you really want to keep mixed salt water in storage is to add a small pump to it. Keep it mixing should keep the alk in solution.
 

Uncle99

Well-Known Member
I have a bit of an Alk problem as well, while I can dose to 10, in 24 hours we are 8. This is great information my friends, while not a number chaser, I'd like to keep to keep Alk in the 10 range for better calcification.
It's been a bit since I tested my beginning mix, it's probably low, or something in the tank is really pulling AlK, but the calcium remains always perfect....hum?
 
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