Alkalinity mixes low with various salts

[Gabaghoul]

Here's something I just cant figure out.

I've tried both Instant Ocean (not Reef Crystals) as well as Fritz RPM and in the container I mix these salts which is a 160 gallon Ace Roto-Mold storage tank made from polyethylene, the alkalinity comes in around 6.5 to 6.8 with a salinity of 1.025. I make a batch once a month when reservoir is empty and these results are pretty consistent. The water I use to mix with the salts is RO produced from my AquaFX unit.

Any thoughts on why this may happen? Could it be residue left from the previous month mix affecting the new batch alkalinity reading? Its quite frustrating because it takes me days to get it in line with where I want it to be, around 8.3.

Any help would be much appreciated.

 

[Gabaghoul]

Well the container is used for my AWC. The test kit I use is Hanna. My main reef with the Hanna measures 8.3 with that test. I have a Red Sea test kit as well. Let me try that test now and see what I come up with. I can also make a batch in a gallon bucket and see what the difference comes out to be.

Have you ever seen the residue from previous mixes affect your alk in new batches?

 

[Gabaghoul]

So I tested Fritz in another bucket for fresh RO. Got a reading of 7.5 on Alk using the Hanna. I guess its never gonna be all that consistent from mix to mix.

On the subject of loosing alk, should I only mix the salt for only an hour or so and then shut it down. I was actually leaving the pump on all night. Sounds like that maybe an issue.

 

[Randy Holmes-Farley]

There’s no reason to continue to stir if there isn’t organic matter such as vitamins in the mix. Heating is the concern, and not heating may also help mixed store with reduced precipitation.

Whether precipitation happens and to what extent likely depends on the CO2 level in the air around the new salt water.

 

[brandon429]

I have a question about extended mixing. have read that on forums for a while now and wondered why would it matter how long a set of water is mixed when we are about to add it to an ever-mixing tank? I can't fathom any changes or precipitations that would occur from motion even if a mixing bucket as zero biological demand for the components vs a tank?

 

[Gabaghoul]

There’s no reason to continue to stir if there isn’t organic matter such as vitamins in the mix. Heating is the concern, and not heating may also help mixed store with reduced precipitation.

Whether precipitation happens and to what extent likely depends on the CO2 level in the air around the new salt water.

Thats a good point. It is possible my garage has a good amount of CO2 and that in turn could cause the precipitation. I never knew CO2 could do that. I thought it only affected pH.

 

[Randy Holmes-Farley]

Salt mixes lack some of the components that reduce the abiotic precipitation rate, such as phosphate and organics, so precipitation may be faster in mixed than in tanks, but it also happens both places.

The mixing is a red herring . Mixing matters not at all. It is heat from the method of mixing that can induce precipitation in mixed with high alk and calcium and perhaps that are formulated to excessively high pH.

 

[Gabaghoul]

You bring up another good point. Is there anything I can do to prevent the precipitation of alk? I usually mix all 160 gallons at once. I start by adding water to the empty container as I add salt as the container fills. Should I do only a little bit at a time, say 40 gallons at a time? I'm surprised others dont have this issue. It seems like it would be common. I tried Instant Ocean as well as Fritz with the same exact results.

 

[Randy Holmes-Farley]

You bring up another good point. Is there anything I can do to prevent the precipitation of alk? I usually mix all 160 gallons at once. I start by adding water to the empty container as I add salt as the container fills. Should I do only a little bit at a time, say 40 gallons at a time? I'm surprised others dont have this issue. It seems like it would be common. I tried Instant Ocean as well as Fritz with the same exact results.

It is common to get some precipitate in new salt mixes with high alkalinity.

What is that Precipitate in My Reef Aquarium? by Randy Holmes-Farley - Reefkeeping.com
http://reefkeeping.com/issues/2005-07/rhf/index.htm

from it:
Figure 1. The residue on the bottom of the plastic trash can that I use to mix Instant Ocean. I rarely clean it out. The solid is most likely calcium carbonate.

 

[aeras1131]

@Gabaghoul what are you mixing your salinity too. Are you mixing it and testing your water to against the stated params. How long are you letting your water sit? I usually mix my SW 1 day prior to WC to minimize precipitation. I use Red Sea Blue Bucket. I do not chase juiced params anymore. I would rather dose proactively because I have the infrastructure to make that for me. Honestly unless you have fast growing corals and lots of them. You are probably going to get a lot of ALK/Ca/Mg Consumtion. Obviously, I would still monitor.

 

[Gabaghoul]

@Gabaghoul what are you mixing your salinity too. Are you mixing it and testing your water to against the stated params. How long are you letting your water sit? I usually mix my SW 1 day prior to WC to minimize precipitation. I use Red Sea Blue Bucket. I do not chase juiced params anymore. I would rather dose proactively because I have the infrastructure to make that for me. Honestly unless you have fast growing corals and lots of them. You are probably going to get a lot of ALK/Ca/Mg Consumtion. Obviously, I would still monitor.

I mix to 1.025. Not trying to chase anything except anywhere between 8 and 9 on the dkH scale. I usually mix the water a day before I start using it as well. I turn on my mixing pump and start dumping salt in. Every 30 minutes or so I check the salinity. Once it hits 1.025, I check for alk. In both cases - IO and Fritz - came in around 6.6. So I boosted them above 8 so they were usable. And then I turn my AWC system back on. Like I said, I'm not chasing a particular number. Just want stability in that range I mentioned above.

I have a feeling Randy is right about the heat precipitating the alk. The water, from the chemical reaction that occurs when mixing, gets fairly hot and that alone could be the issue.

Can I ask, what do you mean by "dose proactively"? You mean to get your mixed water to your ideal numbers before adding to the tank or once you have done the water change, adjust your dosers to compensate?

 

[aeras1131]

@Gabaghoul Personally, I do not mix my water with a pump. My salt mixes to the numbers on the bucket. Maybe patience and a bubbler/agitator will minimize heat based alk precipitation. I agree with Randy's hypothesis on the whole. Would you be interested in testing it out. Perhaps mix your water without the wavemaker/powerhead and see what the alk mixes out at 1.025 salinity? If you are letting your water sit for a day. It should completely mix out clear by the end of the 24 hours. Personally I mix out my salinity to really close to the desired salinity. I will let the saltwater clear, I will do a final salinity test after a brief stir. What I mean by dosing proactively is this, I measure what my consumption rate is of my my big three Delta Consumption/Day. I then does daily to compensate for that consumption/day. Because of this, my params will stay on point long term as long as I am consistently mixing my salt. I do not run into the issue you are running into but I do not agitate my water to mix my saltwater. I just mix, measure, and let it sit for a day.

 

[Gabaghoul]

Yeah, for sure. I'm almost done with this month's supply of water. (I do AWC @ 6 gallons a day. Its takes me 27 days to use the 160 gallons). When its done, I'll mix with an air pump I have here instead of the PanWorld pump I usually use. Hopefully, thats it. That would be awesome. I'll let you know how it goes. Thanks.

 

[aeras1131]

Keep me posted

 

[Gabaghoul]

Well, it looks like reducing the amount I used the Panworld pump to mix helped quite a bit. I only used the pump to stir the water for about 1 at a time a few times throughout the day, making sure not to create any heat, then I tested. Alkalinity of the Fritz mix came out to 7.6, which was a lot higher then I was getting before(6.5). I added some soda ash solution to get me back up to around 8.3 and continued my AWC. I'm fine with that.