Alk issue — using distilled water in ATO

[2willdo]

Hoping I can get some advice on an issue with Alk (and associated pH).

 

My IM Fusion 30 finished cycling back in March and contains a handful of zoas and a couple of LPS transferred over from a Fluval Spec V zoa garden. I used Caribsea LifeRock and the Reeflakes substrate.

 

I am using Fritz RPM salt mixed approx. 24 hours under a powerhead in distilled water purchased from Walmart. (I don’t have an RODI option currently). I know that distilled becomes somewhat acidic very soon after distillation is complete and after air hits it. I am now wondering if the salt mix alone is not enough to maintain Alk ideal levels? I used this same salt brand and distilled water in my little Fluval Spec V and never had this issue, but 5 gal. vs. 30 gal. is 6 times the difference. Is it possible the greater volume of water accounts for the rapid Alk drop and/or the higher evaporation rate (using distilled in an ATO container that is well closed up except for a small opening for the plumbing and pump wire).

 

I’ve been testing the chemistry at the same time every day and it keeps dropping steadily. This morning Alk was at an all-time low of at 6.5, pH was 7.6. Getting ready to do yet another 25% tomorrow morning. When freshly mixed the Alk measures 11 (and the pH is 8.2) using a Salifert kit.

 

I have the returns pointed upward so they agitate the surface of the water, but that hasn’t helped. The aquarium is in our den in SW Florida, closed up because of the AC but the ceiling fan runs all day in that room. I read elsewhere in the forums here that pH changes actively throughout the day (and not to “chase” it); and it is more important to maintain healthy Alk levels. I am not experienced with dosing systems but am I going to have to go that direction?

 

Other params are NO₃ 5; Phos 0; Ca 435, Mg 1320, SG 1.024, temp 74° F.

 

Again, forgive the long post… and thanks for any advice you might have.

[Clown79]

There should be nothing in distilled to change alk. It's pure water, no minerals. Same as rodi. 

 

My alk and ph was never different using distilled vs rodi. What made the difference was the corals housed in the tank. Lps use up alot of alk.

 

You will have more alk consumption in a 30g than 5g because you have more sand, rock, coralline, and corals using it.

 

Is that salt brand meant to be mixed for 24hrs, not all brands need or can be mixed for that long.

 

How long do you store mixed salt water before use?

[Garf]

Are you keeping the powerhead running the entire time in your 24 hour mix? Don't think it is supposed to be mixed for an extended period. I only run powerhead for 30, 45mins max, moving powerhead around a couple times during the mix. Then drop in a heater to raise it to near tank temp, then dump the water in within the next hour or so. I am only doing 1-2 gallon changes though. Also using Fritz RPM. 

 

Also, you say your mix tests dkh at 11 using salifert, that seems high for Fritz RPM (mine is near 9 dkh). I'd make sure the dry salt was thoroughly turned over a few times to make sure it hasn't settled out. 

 

What kind of LPS do you have, how big? I can't imagine they are taking up that much alk, water changes should keep you steady. 

[2willdo]

27 minutes ago, Clown79 said:

Is that salt brand meant to be mixed for 24hrs, not all brands need or can be mixed for that long.

I just looked at the label... something I missed.... it says on the bag to wait 2 hours before using it for a water change. I just turned off the pump, it's been running about 6 hours... maybe just maybe?

 

How long do you store mixed salt water before use?

I use it immediately, I don't store water. The instructions say you can though, but to check Alk before using. Hmmmmm.

 

Thank you Clown79, these were things that had not occurred to me, appreciate the insight.  😀

 

[2willdo]

28 minutes ago, Garf said:

Are you keeping the powerhead running the entire time in your 24 hour mix? Don't think it is supposed to be mixed for an extended period. I only run powerhead for 30, 45mins max, moving powerhead around a couple times during the mix. Then drop in a heater to raise it to near tank temp, then dump the water in within the next hour or so. I am only doing 1-2 gallon changes though. Also using Fritz RPM. 

Clown79 brought that up too. I used to use another brand that took forever to mix, it became a habit to let it go for a day before using it. I just turned off the powerhead after 6 hours, going to check the Alk again in a few minutes to see if it has changed.

Tank is at room temperature, 74 degrees, no need to heat it here. Fresh mixed water is sitting next to tank at room temp also, everything matches temp-wise. In fact I have a chiller at the ready in case of any AC problems in the house. I always had to use a heater in Colorado, Florida is a whole 'nuther animal (literally).

 

Also, you say your mix tests dkh at 11 using salifert, that seems high for Fritz RPM (mine is near 9 dkh). I'd make sure the dry salt was thoroughly turned over a few times to make sure it hasn't settled out. 

I always shake the mix very well before using it, but that is a good point. Going to test it again... looking back at my tank journal (since March) it looks like the Alk has been ranging from 9-11... maybe I have a bad batch of salt?

 

What kind of LPS do you have, how big? I can't imagine they are taking up that much alk, water changes should keep you steady. 

One small blasto, about 1 inch or so across, a two-headed duncan on a frag plug and a hammer about 4 inches across when fully extended. In a 30 gal. tank it wouldn't seem like so few corals would be using so much but maybe?

 

I keep wondering if it is the evaporation rate... the makeup water diluting it... but then again wouldn't the other elements also be reduced?

Thanks for the help Garf, appreciated.