Jump to content
realypk

Need help calculating salt usage...

Recommended Posts

1 hour ago, bues0022 said:

 

 

 

I'm not so sure you've fixed the entirety of your problem. As Tom said, you're "missing" enough salt for 13 gallons of water. You skim 1/2 gallon every 2 days. In 2 weeks, therefore, you've skimmed 3.5 gallons. That's only 1/4 of the missing salt. 

 

If the last statement I have you quoted in here represents how/where you think the majority of the missing salt went, then I think there's still another explanation. I've had my tank before where after a water change I would have sworn I had one reading, only to take it a second time and get another. Bubbles on the refractometer will make results goofy - even little ones I've seen skew it. I always take at least 2 different readings before I start trusting it.

 

Another piece of that is the exaggerated total water volume as well. Something else to keep in mind is the accuracy of the Hanna checker. When combined, I think the real culprit is the skimmer (1/2g per day on a 75g is crazy). 

Edited by madweazl

Share this post


Link to post
Share on other sites

If skimmate was lighter than what is pictured, then you're definitely skimming wet. If you had lower water volume, then the amount lost would scale linearly. That could be a source of error. If you're using a regular refractometer, then you may have been estimating where the line is and that can have error in it, too. The idea behind the analysis was not so much absolute accuracy, but to highlight that you had a possible major export of saltwater somewhere that was being compensated for by your ATO. As madweazl noted, a half gallon a day of skimmate from a 75 gallon tank is an awful lot. 

 

Whether you want to go with a three-part replacement or the ATI method is a personal choice. A regular two/three-part approach has a long history of success worldwide, but the Balling method (of which the ATI method looks similar to) has a history of success, too (in Europe, especially). 

 

Anyway, dial that skimmer back in whatever way makes sense and you'll probably see this problem go away. 

Share this post


Link to post
Share on other sites

The accuracy of my work with the refractometer is very much in question, the accuracy of my hannah digital is not really in doubt because its always 100% spot on.

 

With the Skimmer is successfully dialed back I managed to get the main water/bubble line down just a few mm below the neck of the skimmer body where the collection cup goes into. So far it seems to be netting an 1-2oz of skim per day... also I've noticed having to refill my ATO reservoir far less and havnt yet had to empty my skim reservoir. Salinity is now at 1.026 for the 3rd day since making the skimmer changes. 

 

Also I just measured my fill line on the refugium which is a custom 55 gallon refugium. It is filled to about 45 Gallons. My 75 Gallon when accounting for sand has a total estimated water volume of 68 gallons when accounting for sand. Not sure how to account for rock, I have about 90lbs of live rock in it also i'm not accounting for the the 1.5" PVC pipes nor the overflow, not sure how to do that.

 

Total estimated water volume is 113 Gallons +/- rock, pvc and overflow.

 

I'll keep testing salinity daily and keep everyone apprised.

Edited by realypk

Share this post


Link to post
Share on other sites
2 hours ago, realypk said:

The accuracy of my work with the refractometer is very much in question, the accuracy of my hannah digital is not really in doubt because its always 100% spot on.

 

With the Skimmer is successfully dialed back I managed to get the main water/bubble line down just a few mm below the neck of the skimmer body where the collection cup goes into. So far it seems to be netting an 1-2oz of skim per day... also I've noticed having to refill my ATO reservoir far less and havnt yet had to empty my skim reservoir. Salinity is now at 1.026 for the 3rd day since making the skimmer changes. 

...

I'll keep testing salinity daily and keep everyone apprised.

Great news! It sounds like things will behave much more reasonably from here forward.

 

BTW, that salinity meter actually measures conductivity then translates that to salinity using a conversion table that assumes a certain mix of ions (e.g Millero's landmark studies on saltwater composition worldwide). As the ionic balance changes, you can see changes in various measures used to measure salinity (e.g. PSU/PPT, SG, and refractive index) even though conductivity (uS/cm) might remain stable. Thus, while the meter may be precise, it may not always be accurate. But, barring some long-term shifts leading to ionic imbalance, digital meters (whether measuring conductivity, refractive index, or density), they're close enough for our use.

 

If interested in learning more about how these conversions are rooted in assumptions that most likely don't apply to our tanks, read this article on DIY salinity standards from 2004. It makes my point in giving three different formulas for saline (table salt + water) calibration standards to calibrate three different popular methods used in the hobby to estimate salinity (density (sg), conductivity, and refractive index) to our oft-accepted point of equivalence (e.g. 1.0264 sg = 35 PPT = 53,000 mS/cm). 

 

 

Share this post


Link to post
Share on other sites

Salinity still at 1.026 almost a week into it. So far I would estimate my ato has sucked 2-2.5 gal of rodi, my collection cup is still not even half way full, i'll take a photo when I dump it to compare with your experience. 

 

How much evap would you say a system like mine running at 78.5f temps in a 68f house would have on average? Does about 2.5gal of rodi use seem normal per week?

Edited by realypk

Share this post


Link to post
Share on other sites

On a 90 with a sump, which has similar surface area, I would usually evaporate anywhere from a 3/4-gallon to a gallon a day. However, that was under old-style metal halides which would have caused more evaporation. I think that a half-gallon a day for your system is probably reasonably in the ballpark of normal.

Share this post


Link to post
Share on other sites

Hey everyone I just wanted to give an update on this. Overskim seems to have been the culprit after all as suggested by everyone here. Curent skim collection is now derastically reduced and produces dark pungent skim I cannot see through. I've replaced 1:1 skim collection with fresh mixed salt mix, seems like my collection container now fills about every 2 weeks. 

 

This was great. I just wanted to thank everyone here for the excellent help that was given to me, really helped solve a headache! Also not having salinity shifts has made all my corals drastically happier looking. 

Edited by realypk

Share this post


Link to post
Share on other sites

Glad that it worked out! :thumbsup:

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×