Advanced Water Changes - A Discussion

[Electrobes]

So I consider myself a very diligent and thorough water changer:

The following is performed for my 40Br Mixed Reef Tank:

- I make five gallons of NSW, first by making RO/DI water and then mixing in my salt... like everyone else.

- I then stick in a pretty strong powerhead (Currently a Koralia 3) in addition to an air pump for aeration.

- The water is left to mix for about twenty-four hours in a 77F home (I used to use a heater, but with it being summer it's just unnecessary.

Here's my question: Does anyone go above and beyond this typical prep for a waterchange. I have seen a couple reefers say they mix NSW for up to a week!

I assume those guys are the ones that have those large water mixing stations, but here's my sub-question Does anyone add anything (Bacterial sources, some of their own tank water, etc.) to the NSW?

Are there specific limits on time when adding such things to NSW?

 

[Timfish]

That's a lot more than what I do. If my new salt water sets for any length of time it's 'cause I got distracted by something and walked off in the middle of a water change.

 

[Sparkpaul]

I use Kent reef salt and I dump the salt in the reservoir to mix for an hour to half a day. Then I drain the water in my sump and complete the water change.

 

[d2mini]

Just FYI... NSW usually means Natural Sea Water.
Like from the ocean.

But your procedure is perfectly fine. The only thing you may want to do is double check with the manufacturer on the mix time. Some salts (Like AquaVitro Salinity for instance) says not to mix for more than a couple hours because the salt will start to precipitate. Most salts don't need to be mixed for more than 30 minutes and can then go right in the tank as long as the temp is equal to that of the display.

 

[Electrobes]

Just FYI... NSW usually means Natural Sea Water.
Like from the ocean.

But your procedure is perfectly fine. The only thing you may want to do is double check with the manufacturer on the mix time. Some salts (Like AquaVitro Salinity for instance) says not to mix for more than a couple hours because the salt will start to precipitate. Most salts don't need to be mixed for more than 30 minutes and can then go right in the tank as long as the temp is equal to that of the display.

Haha I can't shake the thought that it's New Salt Water.. doh! This is what I get for not being an active poster anymore.

I am shocked that you could actually overly mix salt into water.. that just sounds crazy to me. I would assume salt would precipitate out if you put too much in... but to overly mix it? Wow. I'm going to have to read up on that, curious to know the science behind it.

 

[bob1435]

I prefer keeping it on hand... So a brute can with a heater and pump in the Basement...

 

[Electrobes]

d2mini - I just checked Aquavitro Salinity's directions for mixing their salt and saw this on their webpage:

Directions
1. Mix salinity™ with dechlorinated tap or purified water. We recommend the use of a commercial dechlorinator like alpha™ to neutralize any tap water chlorine and/or chloramines. If source water quality is poor we recommend purification with a Seachem Pinnacle™ RO/DI system. To prepare small quantities, bring 35 grams of salinity™ up to a volume of 1 liter, or add 36.27 grams to 1 liter of water. [This is a little less than 1/2 cup of salt per US gallon of water. For 15 gallons use 7 cups of salinity™.]

2. Stir well to ensure a good mix. Although the salinity™ solution may be used immediately, we suggest mixing for approximately 24 hours to achieve oxygen/carbon dioxide equilibrium.

3. Measure the salinity. We recommend a salinity of 35‰. This will be a temperature compensated SG (specific gravity) value of 1.026. If you are using uncorrected SG values (H) then the following formula will yield a value for S (salinity) accurate to within 1%:

S = [0.3348 * T] + [1325 * H] - 1330.4525 (calibrated at 15.56 °C (60 °F))

S = [0.2211 * T] + [1325 * H] - 1330.4525 (calibrated at 25 °C (77 °F))

 

[Steveb]

Red Sea Pro Salt

Red Sea Pro Salt

Never mix salt in an aquarium containing animals. Alwaysuse clean, non-toxic utensils.
1. Prepare the quantities of salt and water for the desiredsalinity according to the chart.
2. Use reverse osmosis (RO) water at approximately20°C/68°F. Always add the salt to the water.

3. Mix vigorously (without aeration) for 0.5 - 2 hours, until all of the salt is dissolved and pH has stabilized to 8.2-8.4. DO NOT mix for more than 4 hours


4. Raise the water temp to 25°C/77°F and measure these.g./salinity with an accurate hydrometer/
refractometer. Add salt or water as necessary to achieve the desired parameter.

source: http://www.redseafish.com/uploadimages/user manuals/10116 Coral Pro Salt manual a2012 4P.pdf

I think it just depends on the salt and its always good to review the manufacturers directions for mixing. In this case mixing longer than 4 hours will cause a precipitous drop in alkalinity.

 

[d2mini]

Maybe it was 24hrs. I can't remember where i saw it but the seachem rep was explaining the cause of the gunk left on the walls of mixing containers as precipitate from the salt being over mixed. Some of us (myself included) mix up large batches that lasts for a couple weeks at a time. I was originally letting the pump continually mix the sw so it didn't settle or sit stagnant but apparently you CAN over mix it and cause the precipitation of certain elements. But not the salt in general. Sorry if that's what you interpreted from my overly simple explanation. My bad.

But there ya go... as you can see, each manufacturer should have specific instructions on mixing up their salt.

Personally, i now let it mix for 2-3 hours... if i remember to turn my mixing pump off.

 

[Electrobes]

Well poop, I currently use RSP salt! It would explain the major amount of "stuff" left over in the bucket and pumps after the water change.

Thanks for the info!

Now does anyone know of additional things done by others in mixing new saltwater? Always curious to see what others do.

 

[dkeller_nc]

Actually, it doesn't depend on the manufacturer's salt, it depends on the manufacturer's opinion!

When any ASW mix is dissolved, there is the potential for some precipitation of calcium carbonate, magnesium carbonate, and sulfates. Exactly how much will precipitate sensitively depends on the temperature, the exact concentration of the ions (both metal ions like calcium and magnesium and cations like carbonate/bicarbonate), the degree to which the mix is aerated, and for how long.

Any ASW will reach an equilibrium within about 24 -48 hours if held at constant temperature and with constant mixing.

Some manufacturers give a maximum mixing time to allow for complete dissolution of the salts but also to minimize equilibration with CO2 in the air and thus prevent precipitation of "enhanced" concentrations of calcium and alkalinity. Other manufacturers have a different philosophy - that the saltwater should be in equilibrium when added to the tank.

That's my personal philosophy as well - I mix the ASW and let it circulate with a powerhead. I don't aerate it - I'd like to prevent evaporation and humidity accumulation in the air through use of an air pump. It might go as much as a week before I use it, but it always is circulating at tank temp for 24 hours before its used.

 

[Steveb]

Actually, it doesn't depend on the manufacturer's salt, it depends on the manufacturer's opinion!

When any ASW mix is dissolved, there is the potential for some precipitation of calcium carbonate, magnesium carbonate, and sulfates. Exactly how much will precipitate sensitively depends on the temperature, the exact concentration of the ions (both metal ions like calcium and magnesium and cations like carbonate/bicarbonate), the degree to which the mix is aerated, and for how long.

Any ASW will reach an equilibrium within about 24 -48 hours if held at constant temperature and with constant mixing.

Some manufacturers give a maximum mixing time to allow for complete dissolution of the salts but also to minimize equilibration with CO2 in the air and thus prevent precipitation of "enhanced" concentrations of calcium and alkalinity. Other manufacturers have a different philosophy - that the saltwater should be in equilibrium when added to the tank.

That's my personal philosophy as well - I mix the ASW and let it circulate with a powerhead. I don't aerate it - I'd like to prevent evaporation and humidity accumulation in the air through use of an air pump. It might go as much as a week before I use it, but it always is circulating at tank temp for 24 hours before its used.

Well I can confirm by measurement that at least in the case of Red Sea Pro salt, if I mix for 24 hours or longer the alkalinity drops from 11ish dkh to anywhere from 6.9 to 8.9 dkh measured with Salifert (depending on temp and length of time mixed). In addition the calcium drops as well but I haven't recorded those numbers.

 

[dkeller_nc]

Yep - that's what I mean about the manufacturer's opinion - the ionic mix of seawater is extremely complicated, and jacking up a particular concentration of one or more ions can make for an unstable mix that won't persist under conditions of aeration and/or mixing. In my case, I want the seawater I use for water changes to be at equilibrium, but others may have a different opinion.

 

[sirreal63]

Curious here but what is the difference in mixing for 4 hours in a container and then putting that water in your tank, where it will continue to mix? If the alk is dropping in a mixing container, won't it also drop in the aquarium?

 

[mr.maroonsalty]

^^***^^ what he asked!

 

[Sparkpaul]

This just got more interesting/confusing.

 

[Steveb]

Curious here but what is the difference in mixing for 4 hours in a container and then putting that water in your tank, where it will continue to mix? If the alk is dropping in a mixing container, won't it also drop in the aquarium?

Yeah I don't understand it myself but I have observed/measured it.

I assume its a function of a bunch chemistry going when first mixed and that is in more of an equilibrium in the tank.

I do know its at advertised (or close) alkalinity at the end of 4 hours. When I kept my tank at a higher dkh that is when I would stop mixing. Now that I'm shooting for 8.9 I let go overnight. The next day if I leave it mixing it has dropped anywhere from 2-4 dkh and there are lots of deposits on the bucket and pump (which is obviously a waste but its what I have right now) .

 

[Electrobes]

Oh Lordy this got a lot more fun!

My tank regularly suffers from a low kH, it's pretty stubborn at around 7. I have measured RSPC salt mix after a 24 hour mix (When I open up a new bucket to check for a bad batch). It's usually at the 8-9 area.. which was unexpected. I would get a slight bump in Alk, but it would saunter back down to 7 pretty quickly.

In an effort to get more consistent with my Alk, I then started using dosing pumps on my Apex at around 10mL per day of TLF's Part B (Alk). I finally have gotten a consistent reading of 10 (And my pH climbed to a more comfortable level), but wonder how that would change if I did either of only mixing for four hours and not aerating the RSPC's salt, or changed to another brand with a more balanced/lower params salt.

I just opened my current bucket, so I will give their instructions a try after my bucket and two pumps finish their vinegar bath.

 

[d2mini]

Curious here but what is the difference in mixing for 4 hours in a container and then putting that water in your tank, where it will continue to mix? If the alk is dropping in a mixing container, won't it also drop in the aquarium?

Good question, Jack.
Maybe they are assuming a much more furious mixing in the separate container mixed with much more air? Maybe there are other elements in the tank that prevents or slows down the precipitation?

 

[Electrobes]

I emailed them this letter:

Hi,

I have been using RSPC salt for the past two years, and just yesterday discovered something that truly shocked me. It seems I have been mixing this salt as suggested for the vast majority of salt... and unfortunately it is not as instructed for mixing RSPC salt.

I mix up a five gallon batch of ASW (Artifical Salt Water) every week for use of a water change. I do the following:

1 - Make five gallons of RO/DI water.

2 - I currently use two pumps for mixing ASW, at the same time: A Koralia 3 and a Maxijet 1200 with the air intake installed (To blow air into the water while mixing).

3 - I slowly pour the salt into the bucket as the water is being mixed with the two pumps.

4 - I let it mix for about twenty four hours in my home, at 77 degrees Fahrenheit.

5 - I then perform the water change.

My problems over the last two years, but ignored because my reef aquarium (A 40Br) never showed ill effects:

1 - My bucket and both pumps are covered in a white chalky substance PER mixing. To clarify, after just one mixing, my mixing equipment is absolutely covered, to the point where I often have to cleaned it out with a cleaning brush.

Discovery!

I was asking about various methods of making ASW for water changes when I was informed that specific salts had to NOT be mixed past a certain point in time, and that they should NOT be aerated. He told me Aquavitro Salinity was an example. I believed it to be false, and looked it up.. and sure enough I was correct... breathing a sigh of relief.

It turns out, he merely got the wrong salt.. it was RSPC salt! I was devastated, crying in a corner realizing the failure I was at being a Reefing God. Okay, no, not really but I was honestly surprised that conventional wisdom for mixing ASW didn't apply, at all, for RSPC salt.

Questions:

1) What is that chalky substance leftover on my pumps and in my bucket?

2) What effects did overly mixing (Via length of time) and aeration have on the ASW. What's the difference between a properly mixed batch of ASW versus what I have been doing the last two years?

Thank you!!

Christian