Rapid salinity drop.

[MrApplebee]

I am a week into cycling my 460 litre (soon to be) reef tank with 50kg of cured live rock and Caribsea Arag live sand. The temperature of the tank is 25c. I don't have the skimmer running on the tank yet. The flow in the tank is from the pump which is set to 1500 lph and 1 vortech mp40 which I have set on full blast at the moment. I use a Red Sea refractometer to check salinity.

Anyway, I bought my salt water ready mixed from my LFS and the salinity was 1.025

Whilst trying to setup my Tunze osmolator (ATO) last week I had a few issues with it and dumped around 20 litres of RO water into the system while I was trying to get it to work correctly. I tested my salinity after this and it had dropped to around 1.015. So I went and got some salt (H2ocean by DD the aquarium solution). I worked out that I would need a little under a kilogram to bring my salinity back up. So I added the salt to a jug and stirred it with a big wooden spoon and poured it in the tank. Waited a while, took a reading and the salinity hadnt budged much. Anyways, I eventually managed to get it up to 1.021 after a Mixing a bit more salt. (A lot more than I'd anticipated I'd need to)

I had to go working away for the week then and when I returned today the salinity was still at 1.021. SO, I added some more salt using the jug and spoon and got the salinity up to 1.025. I just tested it again 3 hours later and it's gone down to 1.021.

My ATO hasn't even added any RO in that time as there has been no significant evaporation so I know it's not that. I have searched everywhere for some kind of leak (even though no water has left the system judging by the levels in the sump and ATO chamber)but can find nothing.

After reading up a bit, which I should have done before hand, I see that people mix their salt water over quite long periods of time using power heads in barrels and stuff.

Where should I go from here? Am I right in thinking that my salt may have settled in the substrate from the water column? Would this explain the initially ok reading from the sample that I took from the water column and then the sudden drop a few hours later?

How long could it take for the salt to dissolve? I've left my mp40 blasting along the substrate for now. I'm worried if I add anymore salt I might end up with my salinity off the scale when the salt that I've previously added finally dissolves.

Feel like an idiot to be honest but could use some advice.

Thanks guys

Mike

 

[Sk8r]

To get back to normal, mix up (24 hours with a mixing pump (any small pump)) some 1.024 salt water (1 gallon salt mix to 32 gallons of water or half a cup of salt mix per gallon of water, by Oceanic and IO instructions) ---
Then as evaporation takes water from your tank 'top off' with the salt water. Once your tank water is 'right,' stop topping off with salt water and only top off with fresh water.
As for salt that may be in the sandbed, I'd say it should fully dissolve after, oh, 36 hours.

 

[reeferdude710]

how come it dropped that low slowly increase if you got fish

 

[Tripod1404]

Two questions, is your refractometer calibrated with a 35ppt calibration solution? ,and, Did you measure the salinity of the pre-made saltwater from the LFS?

Yes you should never add un dissolved salt to an aquarium. I doubt undissolved salt will remain in your tank for more than few days (unless large amounts of it gets under the sand and somehow gets sealed away). But when you have live stuff, salt crystals landing on top of them would cause great harm. Like you said, dissolve it in a barrel the night before and use that water.

Measuring salinity immediately after adding the salt can give false readings since there would be suspended solid particles in the water that did not dissolve yet. When I am preparing saltwater, I dont make measurements before at least several hours have passed since I added the salt.

For now, turn off the ATO and manually top off the evaporated water with saltwater. This way salinity will slowly increase. After you reach your desired salinity level, you can turn the ATO back on

 

[MrApplebee]

Two questions, is your refractometer calibrated with a 35ppt calibration solution? ,and, Did you measure the salinity of the pre-made saltwater from the LFS?

Yes you should never add un dissolved salt to an aquarium. I doubt undissolved salt will remain in your tank for more than few days (unless large amounts of it gets under the sand and somehow gets sealed away). But when you have live stuff, salt crystals landing on top of them would cause great harm. Like you said, dissolve it in a barrel the night before and use that water.

Measuring salinity immediately after adding the salt can give false readings since there would be suspended solid particles in the water that did not dissolve yet. When I am preparing saltwater, I dont make measurements before at least several hours have passed since I added the salt.

For now, turn off the ATO and manually top off the evaporated water with saltwater. This way salinity will slowly increase. After you reach your desired salinity level, you can turn the ATO back on

Thanks for the reply. In answer to your two questions 1. I'm not sure. I just used the refractometer out of the box, it read the LFS water at the 1.025 they had told me it was mixed to. 2. Yes I checked it and it was 1.025.

Thanks for the advice, can't belive I made such a daft mistake. Lesson learned I guess. : )

 

[MrApplebee]

To get back to normal, mix up (24 hours with a mixing pump (any small pump)) some 1.024 salt water (1 gallon salt mix to 32 gallons of water or half a cup of salt mix per gallon of water, by Oceanic and IO instructions) ---
Then as evaporation takes water from your tank 'top off' with the salt water. Once your tank water is 'right,' stop topping off with salt water and only top off with fresh water.
As for salt that may be in the sandbed, I'd say it should fully dissolve after, oh, 36 hours.

Thanks for the reply. Am I best waiting a couple of days to see where the salinity is? Then follow yours and tripods advice? (Just in case I get the salinity right but then the salt in the sand bed dissolved and raises it)

Cheers

 

[Tripod1404]

Thanks for the reply. In answer to your two questions 1. I'm not sure. I just used the refractometer out of the box, it read the LFS water at the 1.025 they had told me it was mixed to. 2. Yes I checked it and it was 1.025.

Thanks for the advice, can't belive I made such a daft mistake. Lesson learned I guess. : )

You should get 35 ppt calibration solution for your refractometer. It is probably alright for now, but It would eventually need re-calibration.

Dont worry about it, its better to make mistakes before there are fish and corals in the tank .

 

[MrApplebee]

You should get 35 ppt calibration solution for your refractometer. It is probably alright for now, but It would eventually need re-calibration.

Dont worry about it, its better to make mistakes before there are fish and corals in the tank .

I shall order some today. Thanks again and yeh, I suppose you're right. Better I make these silly errors early.

Mike : )