Salinity Creep

[-Logzor]

I'm not sure if anyone else has this issue but the salinity in my system always seems to creep up, especially if I skip water changes for a week or two. I'm fairly certain this is due to impurities in my two-part dosing system that are not absorbed by my corals. My system is 150g + 30g sump and I dose approximately 120mL a day of both calcium and alkalinity, plus I dose limewater at about 50mL a day. The only solution I've found is to conduct weekly water changes or just manually remove some water and then let it top-off.

What causes this problem? I'm using all the high purity ingredients from BRS, it seems that what I dose the corals should use up.

 

[Randy Holmes-Farley Verified Community Expert]

Salinity definitely increases over time using a two part supplement.

It's not really due to impurities, but the way the method is designed.

The two main ingredients are sodium bicarbonate/carbonate and calcium chloride.

The corals use the calcium and carbonate to make calcium carbonate skeletons, but necessarily leave behind the sodium and chloride.

In a well designed two part, what remains is close in composition to seawater, so the ion ratios don't get messed with too much, but the salinity does rise.

Two good solutions are to replace salt water with fresh once in a while, or to do water changes with slightly lower salinity than the tank target value.

 

[-Logzor]

Thanks! Makes perfect sense, never thought of it that way.

 

[Randy Holmes-Farley Verified Community Expert]

You're welcome

Happy Reefing!

 

[AquamanE]

Man i love following Randy. Makes sense.

Randy - wouldnt Logzor benefit from adding more limewater, ie all depleted evaporation, allowing him to decrease the 2 part? Wouldnt that decrease the salt creep?

 

[-Logzor]

Man i love following Randy. Makes sense.

Randy - wouldnt Logzor benefit from adding more limewater, ie all depleted evaporation, allowing him to decrease the 2 part? Wouldnt that decrease the salt creep?

I considered that, actually, mostly to maintain higher pH. Does limewater leave behind less "stuff"?

To be perfectly honest I'm getting sick of these lazy corals leaving behind all that crap in my water.

 

[AquamanE]

I will of course let Randy give the final answer, but this is where I have gotten and successfully used my opinion on this.

What Your Grandmother Never Told You About Lime by Randy Holmes-Farley - Reefkeeping.com

In this article, check the paragraph in the bottom, that mentions "limitations of limewater". If your tank allows you to meet its demmands with just limewater, then no need to dose 2 part is necessary. 2 part is more expensive. If your tank requires even more then 2 part can be started.

I have a 200 gallon SPS dominant tank. All my evaporated water is replaced with saturated lime. My tank needs more so i supplemment with 2 part. I currently add 52 ml's of each per day.

 

[-Logzor]

I will of course let Randy give the final answer, but this is where I have gotten and successfully used my opinion on this.

What Your Grandmother Never Told You About Lime by Randy Holmes-Farley - Reefkeeping.com

In this article, check the paragraph in the bottom, that mentions "limitations of limewater". If your tank allows you to meet its demmands with just limewater, then no need to dose 2 part is necessary. 2 part is more expensive. If your tank requires even more then 2 part can be started.

I have a 200 gallon SPS dominant tank. All my evaporated water is replaced with saturated lime. My tank needs more so i supplemment with 2 part. I currently add 52 ml's of each per day.

Do you run though a kalk reactor or just mix in your top-off container? How do you ensure the water is saturated if you add to your topoff with no reactor?

 

[AquamanE]

I will of course let Randy have the last say, but here is how I have been doing it for the past 8 years.

I have an 18 gallon Brute. I mix 1.5 tsp per gallon of ro/di water ( this or 2 tsp/gal is the saturation dose for lime/gal). I stir it agressively for a few minutes. Once it has settled, i have it hooked up to a diaphragm pump (aqualifter) and to a auto top off.com float switch (two switches one is a safety switch). At the input side I have it on a 1" PVC ( that keeps the intake water above the settled lime). Basically a line attached to a 1" pvc with a rubber-band. I let this feed the tank of all evaporated water.

Of course this is not enough for my tanks demand so i supplement 2 part, but on a much lower dose than if it wasnt for the limewater. Im not a big fan of reactors since you add another element of potential failure. But thats my opinion.

 

[Randy Holmes-Farley Verified Community Expert]

Man i love following Randy. Makes sense.

Randy - wouldnt Logzor benefit from adding more limewater, ie all depleted evaporation, allowing him to decrease the 2 part? Wouldnt that decrease the salt creep?

Thanks.

Limewater is a fine choice (I use it alone), and it causes no rise in salinity over time.

It does cause a very slow rise in calcium over time, relative to alkalinity, because it doses calcium and alkalinity in the exact proportions in calcium carbonate, but any calcium carbonate formed in the tank will have some magnesium (and even less strontium) incorporated in place of calcium, leaving some extra calcium behind. I use a low calcium mix 9Instant OCean) for water changes and I never boost calcium otherwise.

 

[Randy Holmes-Farley Verified Community Expert]

Do you run though a kalk reactor or just mix in your top-off container? How do you ensure the water is saturated if you add to your topoff with no reactor?

I know the question wasn't aimed at me, but when I mix it in a barrel, it is easy to ensure saturation just by adding excess calcium hydroxide, or by monitoring the conductivity (about 10.3 mS/cm is saturated at 25 deg C), and I aim for 8-9+ mS/cm or so). I actually think one can control the amount dissolved in this way more readily than in a reactor. I mix it up about once a month and it is good to go.

 

[-Logzor]

I know the question wasn't aimed at me, but when I mix it in a barrel, it is easy to ensure saturation just by adding excess calcium hydroxide, or by monitoring the conductivity (about 10.3 mS/cm is saturated at 25 deg C), and I aim for 8-9+ mS/cm or so). I actually think one can control the amount dissolved in this way more readily than in a reactor. I mix it up about once a month and it is good to go.

Good to know! I measure the salinity in the aquarium with conductivity anyways.