Puzzling problem about salinity?!

[whiterabbit.50]

Hello,

I was just making some water for a water change and im having a major problem getting it to the right salinity.

Im using a ro/di filter to fill 5 gallon buckets, into which I mix my red sea salt mix. I just got this ro/di filter made by purely h2o and this is the second time making water.

What im confused about is that after mixing the salt and letting dissolve overnight I went to test it and instead of being at 1.023 like the instructions say, it is at 1.010.

I use a recently bought refractometer to test the salinity. I double checked its accuracy by testing the water in my tank, which it shows correctly to be 1.025, and I tested it with its calibration fluid and it correctly shows 1.000, as well as testing it against unmixed ro/di water which it also shows to be 1.000.

I have been using this salt mix for a few months now and up to now ive had no problems. I also triple checked that I added the the right amount of salt because I threw out the first batch that the refractometer showed to be 1.010 and remade some last night, making sure that i added the right amount of salt according to the instructions and it still shows 1.010!

Anyone have any ideas as to what could be going wrong?!

thanks!

[Rich D]

maybe the salt isnt totally dissolved in the water and has settled on the bottom of the bucket

[tkeracer619]

What does your swing arm say?

[whiterabbit.50]

I checked that theres no salt at the bottom of the bucket, and I dont have hydrometer to compare it too.

I also made sure the let the water sit on the refratometer for a couple of minutes to equalize the temperatures.

[tkeracer619]

You don't need to balance any temps.

2.5 cups of your salt mix = 1.010?

What did you use before you got the refractometer to test salinity?

Generally you calibrate refractometers with a solution close to that of sw not 1.000

[whiterabbit.50]

The refractometer said it was calibrated in the factory and came in a air tight sealed bag. Its made by sybon and the instructions say that you dont need to calibrate it for some time. The solution is ultra pure at 1.000.

my salt mix said 1.4lbs for 5 gallons to get 1.023 and thats what i put, it was one tall cup full of salt. (yes i made sure to to take the weight of the cup in my measurment)

I had the refractometer from day one. I tried a hydrometer but it was really crappy and returned it back to the store.

[Toddrtrex]

What solution are you using to calibrate your refract? Most of the solutions that I am aware are should read 1.026 and not 1.000.

[BuddhaKiss]

The directions on my refractometer said to calibrate it with distilled water which should read 1.000. Have I been doing it wrong this whole time?

[whiterabbit.50]

the solution says ultra pure water. the instructions say that it should read 1.000. i know its not the MOST accurate way of calibrating but it cant make my refractometer be off by .01! the refractometer im using is only a 2 months old, and came pre calibrated. not only that but it reads the salinity of my tank at 1.025 constantly for the past two months.

also, the bucket that im using is one from instant ocean salt mix. its been washed and clean. im wondering if the the rodi water ate away at the buckets plastic making it absorbant and therefore the bucket absorbed some of the salt. is this crazy?

[Toddrtrex]

<a href=showthread.php?s=&postid=14456653#post14456653 target=_blank>Originally posted</a> by BuddhaKiss
The directions on my refractometer said to calibrate it with distilled water which should read 1.000. Have I been doing it wrong this whole time?

If you are using distilled (( or RO/DI )) water, then 1.000 is correct. But, if you are using a calibration fluid (( like the pinpoint one )) would want to calibrate to 1.026/35 PPT. The calibration fluid is more accurate.

[dwd5813]

a refractometer calibrated to 1.000 will not read seawater properly. it's a good first step, but the device ultimately needs to be calibrated to read in the range we use. i suggest reading this (http://reefkeeping.com/issues/2006-12/rhf/index.php) article about salinity and refractometers.

[whiterabbit.50]

i totally agree with you guys about calibrating with a solution that is 35 PPT and that it is more accurate then using distilled water. I will look into getting one.

but, can my refractometer be .01 off just because i use distilled water for calibration? that would make my tank water be 1.036, which would most certainly have killed the two clowns and shrimp i just added after only a 1 hour drip acclimation. im pretty confided that my refractometer is right, since it has been measuring my tanks water at around 1.025 for the past few months.

any other ideas as to why my salinity is so off with my top off water?

[luther1200]

Maybe you have a little bit to much water in the bucket.

[whiterabbit.50]

the buckets only hold 5g.

I just added some more salt. I have now put almost double what the instructions say and what I have done in the past. The sg is now 1.025. I think Ill use this water because I trust my hydrometer more then the salt.

If anyone has any idea as to why I needed to double the amount of salt to get this sg I would love to hear them. I think ill just buy a bucket of Instant ocean and try that.

[dwd5813]

i'm not totally sure on the level of inaccuracy possible, since that's based on several factors but at 5 bucks a bottle, http://www.drsfostersmith.com/product/prod_display.cfm?c=3578+4416+18717&pcatid=18717, i'd get the refractometer calibrated properly before using water that you've dumped all that salt in. the only reason i can imagine you've felt you needed to use twice your previous amount of salt is measuring error. did you leave the salt uncovered? is it clumped up in it's container and/or not fully dissolved in the water?

[RandomHero426]

I use the red sea salt and I have to add a lot more than the directions state....probably almost double and I have both a swing arm and refractometer

[Hop]

So add salt?

I'm confused what the problem is exactly... If you test the tank with the refractomer and it shows 1.025 and then you test the WC water and it reads 1.010, you need to add salt in order to bring it up...

A lot of good info on calibrating the refractometer, but the solution seems so easy it's being overlooked:lol: And the bucket probably holds more like 6 gallons... If it is an old salt bucket. Match the tank water and worry about proper calibration down the road...

[whiterabbit.50]

the salt in the bag looks ok, i always close the bag/box up tight when storing it. I will look into getting a proper calibration fluid.

What is really weird is that I never had to double the amount of salt when making water before. and I have been using the same refractometer the whole time. the only thing that changed is the ro/di unit that I got, but rodi water is rodi water right?

thanks for the help!

[whiterabbit.50]

i did just add some salt, but I really want to know what went wrong. I have never ran into this problem before and I haven't changed anything in my procedure.

[snorvich]

<a href=showthread.php?s=&postid=14456684#post14456684 target=_blank>Originally posted</a> by Toddrtrex
If you are using distilled (( or RO/DI )) water, then 1.000 is correct. But, if you are using a calibration fluid (( like the pinpoint one )) would want to calibrate to 1.026/35 PPT. The calibration fluid is more accurate.

Amen. Actually pinpoint fluid is 1.0264. Most refractometers should not be calibrated with distilled water.

[Hop]

I don't think anything went wrong. It's hard to say... I mix between 40 and 200 gallons at a time, so I just keep adding salt til I'm at the proper sg;)

[snorvich]

<a href=showthread.php?s=&postid=14458223#post14458223 target=_blank>Originally posted</a> by Hop
So add salt?

I'm confused what the problem is exactly... If you test the tank with the refractomer and it shows 1.025 and then you test the WC water and it reads 1.010, you need to add salt in order to bring it up...

A lot of good info on calibrating the refractometer, but the solution seems so easy it's being overlooked:lol: And the bucket probably holds more like 6 gallons... If it is an old salt bucket. Match the tank water and worry about proper calibration down the road...

And I agree with this as well.

[dwd5813]

fwiw, i dont really measure the exact amount of salt i put in my water either. i use a 1 cup container and try to put only one of those per two gallons but i'm always adjusting up or down the next day. if you trust your measuring device, just use whatever amount of salt it takes. i'd definitely take the steps to calibrate it properly asap, though.

[tkeracer619]

What kind of salt are you using? 1 cup of salt is generally not enough. Most every salt brand I have used is .5 cup of salt per gallon to get 1.024

[ZoaFan08]

I never measure the amount of salt I put in, I always just add salt till my salinity is correct. If I mix salt 5 times all 5 times will require different amounts of salt.

[luther1200]

5 gallon buckets usually do actually hold more than 5 gallons. So if its filled to the top it might be to much. Thats just a thought though.

[luther1200]

I use reef crystals and I always just put in 2.5 cups for 5 G. Then check it with a refractometer. I have never had to add more.

[whiterabbit.50]

i measured 5 gallons and put a line in the bucket, i dont fill them up to the top.

zoafan, thats good to hear. I will just trust my refractometer from now on and mix the water according to it and not the instructions.

what is still bothering me is that this was never a problem before. I have always measured my salt according to weight, and 1.4lbs gave me 1.023. what i really would like to know is why these two times, and only these two times, 1.4 lbs only gave me a salinity of 1.010?

[Toddrtrex]

<a href=showthread.php?s=&postid=14458335#post14458335 target=_blank>Originally posted</a> by snorvich
Amen. Actually pinpoint fluid is 1.0264. Most refractometers should not be calibrated with distilled water.

I knew there was another digit (( the 4 )), but didn't want to say the wrong one, so left it blank -- thanks.

[eric@tampa]

+1 on luther1200 reply,reefcrystals 1/2 cup per gal. never a problem

[Jerm77]

<a href=showthread.php?s=&postid=14459120#post14459120 target=_blank>Originally posted</a> by whiterabbit.50
i measured 5 gallons and put a line in the bucket, i dont fill them up to the top.

zoafan, thats good to hear. I will just trust my refractometer from now on and mix the water according to it and not the instructions.

what is still bothering me is that this was never a problem before. I have always measured my salt according to weight, and 1.4lbs gave me 1.023. what i really would like to know is why these two times, and only these two times, 1.4 lbs only gave me a salinity of 1.010?


if you are weighing your salt, are you sure that the salt has not taken on any additional weight? maybe from moisture?

[Gwynhidwy]

If you are confident in your refractometer's reading, then add more salt until it reads where you want, keeping in mind salt mixes can take 12+ hours to fully dissolve.

That being said, if nothing else changed and my refractometer started reading odd, I would be double checking its reading against another refractometer as well as calibrating before adding anything to the tank. Most critters we house are surprisingly tolerant, but only so much and for so long. Not double checking is a big risk in my opinion.

[whiterabbit.50]

thanks for all the info.

I think i solved my problem. Because i mixed my salt when the water was still really cold, not all of it dissolved, and even after 24 hours in the basement it was still pretty cold so that is why my reading was off. I measured it again today and the bucket in which I added twice as much salt was at 1.060. I will be investing in a pair of powerheads and heaters to make mixing water alot simpler and quicker.

lastly, I was just topping of a bucket with my RO/DI unit but by mistake I turned on the hot water tap instead of the cold one. The water running through it was hot to the touch. I read about the dow filmtech membranes that their max operating temperature is 113 F (45 C). I let the unit run for 10 minutes before noticing, I dont have TDS meter to test my water but do you think this would have damaged my membrane/di resin?

[dwd5813]

sounds like you found your problems. that's good. unfortunately it could easily have cost you that membrane and di resin but that's a smaaalll price to pay by comparison. i'd go ahead and get new ones just to eliminate the doubts.