Trouble maintaining alk

[krak256]

I've been having some issues maintaining my alkalinity around 9 dkh and was hoping for some insight.

I've been using Coralife salt, which mixes around 9dkh. A few days ago, I tested my tank alkalinity and noticed it was surprisingly low at 6.3 dkh after a 10g water change. I thought perhaps there was an issue with the salt and dosed ~45ml of BRS soda ash. The next day, I did another 10g water change and tested the new water which was at 9 dkh.

I tested the water the next day and the tank alkalinity was only at 6.7 dkh. Assuming my total water volume is only 40g (40g tank + 20g sump - rock and sand), the dkh should be closer to ~7 dkh, correct?

I noticed when I dose the soda ash, it is a bit snowy but it may be related to it dropping into a low flow area of my sump. Does the "snow" mean the alk is precipitating and therefore not increasing my dkh?

Thanks in advance.

 

[ludnix]

Definitely dose it in an area of high flow, that may be part of the cause of your lower than expected readings. The soda ash should make a milky cloud that disappears quickly in the flow. If I am manually dosing I add this to my display near a powerhead, slowly enough so that it is disappearing before spreading around the tank. Additionally, the fact that there is a negative feedback loop when you dose, the corals consume more bringing the level back down. Try testing alkalinity 20 minutes after dosing to ensure its at the right level.

 

[ncaldwell]

HIGH flow is important. I was dosing in a low flow area and was dealing with low all. I put a small pump there and my alk jumped up 4 ppm. Monitor it very carefully after you fix it, lost a few corals with that one

 

[BeejReef]

is your calcium varying in sync with your alkalinity, or is it just your alk?

 

[krak256]

Thanks for the tips everyone. I'll make sure to move the tubing so that it doses in a higher flow area. Would the drain/skimmer area be sufficient?

Calcium generally tends to be more stable.

 

[ludnix]

That should be fine if you see it dissolve quickly enough. Calcium is likely fluctuating similarly but it doesnt appear as severe because of the two are measured on different scales. Coralife usually has higher than desired calcium for me so I rarely dose it when i'm on top of waterchanges. I may switch brands in the future to get readings closer to where I like and make dosing simpler.

 

[BeejReef]

It might be worth testing your magnesium levels as well... something about when mag is too low, calc and alk precipitate out more readily

 

[krak256]

It might be worth testing your magnesium levels as well... something about when mag is too low, calc and alk precipitate out more readily

Thanks, I'll double check my mag to see if it's high enough.

I bought the Coralife because it was on sale. I'll probably use it up and switch back to Instant Ocean or Reef Crystals.

 

[SeaDweller]

I’d test magnesium too. Mg is often forgotten about and can help balance out the issue you’re having, if it is indeed low

 

[krak256]

Just tested and my parameters were:

Alk: 6.4
Cal: 420
Mag: 1440

I dosed about 30ml of soda ash into my drain area and it increased my alk to 7.7. Seems like my prior alk issue was due to low flow?

 

[Reefahholic]

What test kits are you using?

What kind of coral and demand do you have?

If you’re dosing all that Alk, break that dose up and don’t raise more than 1 dKH in 24 hrs.

 

[krak256]

What test kits are you using?

What kind of coral and demand do you have?

If you’re dosing all that Alk, break that dose up and don’t raise more than 1 dKH in 24 hrs.

I'm using Salifert kits. I have a mixed reef but probably more SPS than others. Got it on the alk dosing; hopefully I didn't do any damage with the higher increase.

 

[BeejReef]

What test kits are you using?

What kind of coral and demand do you have?

If you’re dosing all that Alk, break that dose up and don’t raise more than 1 dKH in 24 hrs.

Yeah, that's another important point. Slow and steady with the dosing.. like through a needle valve or an airline hose tied into a knot (like you'd use to acclimate a fish).

 

[The Opinionated Reefer]

Look into using kalwasser. Its cheap and will add calcium and alkalinity in a balanced ratio. It's working wanders for my tank.

 

[The Opinionated Reefer]

Look into using kalwasser. Its cheap and will add calcium and alkalinity in a balanced ratio. It's working wanders for my tank.

 

[krak256]

Look into using kalwasser. Its cheap and will add calcium and alkalinity in a balanced ratio. It's working wanders for my tank.

If my evaporation fluctuates during the summer, isn't this a bit dangerous?


So I tested again today and my alk dropped from 7.7 last night to 6.25. Is this a normal rate of decline? I dosed again and brought my alk back up to 7.0

 

[BeejReef]

That's a pretty sharp decline, but it's all relative. If you have a tank full large coral colonies, it makes more sense.

If you evaporate a bit less in the summer, you would probably notice your tank losing one dkh or so over the course of a week. You could mix more kalkwasser into your ATO or run a fan over the tank to increase evaporation. Depending on how warm it gets, you may be doing that anyhow. In either case, the DKH swings you might expect from the variability of evaporation are far less that the daily 1+ DKH swings you're getting right now.

Do you have a full tank picture you can post?

The alkalinity is going somewhere and it's going there fast. You've checked magnesium. Have you double checked your salinity? Is it possible you have an undetected leak?

 

[krak256]

That's a pretty sharp decline, but it's all relative. If you have a tank full large coral colonies, it makes more sense.

If you evaporate a bit less in the summer, you would probably notice your tank losing one dkh or so over the course of a week. You could mix more kalkwasser into your ATO or run a fan over the tank to increase evaporation. Depending on how warm it gets, you may be doing that anyhow. In either case, the DKH swings you might expect from the variability of evaporation are far less that the daily 1+ DKH swings you're getting right now.

Do you have a full tank picture you can post?

The alkalinity is going somewhere and it's going there fast. You've checked magnesium. Have you double checked your salinity? Is it possible you have an undetected leak?

I don't really have large colonies; it's only a 40g and has lots of SPS but mostly mini colonies/frags. Here is a FTS:

I double checked my alk again last night and it dropped to 6.25 again. I didn't check salinity but I will tonight and update my post.

 

[BeejReef]

Nice tank. Nice corals!

Where are the fish? ;Nailbiting

I hope one of the pros can fig out your issue for you, but whatever you've been doing has been working pretty well.
My limited understanding is that it's near inconceivable for a tank to utilize just alkalinity and not calcium, even though it can look that way bc of how much faster alk drops.
With nice corals like you've got going, might be time to up your game to some sort of sustained, gradual alk/calc solution like limewater or two-part.

 

[krak256]

Nice tank. Nice corals!

Where are the fish? ;Nailbiting

I hope one of the pros can fig out your issue for you, but whatever you've been doing has been working pretty well.
My limited understanding is that it's near inconceivable for a tank to utilize just alkalinity and not calcium, even though it can look that way bc of how much faster alk drops.
With nice corals like you've got going, might be time to up your game to some sort of sustained, gradual alk/calc solution like limewater or two-part.

haha my fish were apparently camera shy when I took the pic.

So my salinity is a bit high, around 1.028/1.029.

I tested my water parameters again:
Alk: 6.0
Cal: 400
Mag: 1440