Aquarium salinity vs natural sea water

Sparrow1617 · Jul 24, 2020

Hi all, I am new to the forum and fairly new to the hobby as well. I have a 650l (170gal) tank+sump setup. Display tank being about 500l (130Gal).

We live close to the sea and when I started of to cycle my tank, I caught a couple of local fish from rockponds. Added a couple of hermits and snails, grabbed a bunch of rocks from the sea as live rock, used beach sand (dried and washed) and off I went. My aim was tosetup a mixed reef tank eventually. Our ocean waters here is quite temperate and the temperatures can get down to about 16*C (61F) with a salinity of about 1.029. Ive always been using Natural Sea Water For water changes. Once my tank cycled, I started to remove the local fish and started adding softies and lps corals. Keeping the salinity at the 1.029. I slowly started to build up a reef tank and ende up with a Scopas tang, Regal tang, 2 Chromis, a clown and a Midas blenny. For crustaceans I had a bunch of hermits and snails (still the local ones) also some local shrimps and 2 fire shrimps. Corals: mushroom, leather, Xenias, GSP, Hammer and a birdsnest. With the NSW, everything looked very happy, they thrived, corals were polyping beatifully, fish was healthy and crustaceans did fine. Then the guy at the LFS told me that 1.029 salinity is too high for any sps and that I need to bring it down to 1.025. I decided to trust the guy as he seems quite experienced and started to do my water changes with 1.025 salinity water to bring down the salinity gradually. This is where my problems started. After the second water change, my Blue tang got whitespot and unfortunately died. I then quarantined my other fish in a hospital tank and started treating with cupramine. 2 days later, my scopas tang died... the other fish seems fine for now but my corals also do not seem to be too happy.

my question is: should I be going back to the ALL natural sea water without diluting the salinity? Or is it good to bring down my salinity to the 1.025?

sorry for the long intro

Randy Holmes-Farley · Jul 24, 2020

How are you measuring salinity?

If it really is that high, I'd bring it down very slowly to about 35 ppt, which has sg ~ 1.0264.

ZoWhat · Jul 24, 2020

Where are you collecting the NSW? From ankle deep water?

Sparrow1617 · Jul 24, 2020

Randy Holmes-Farley said:
How are you measuring salinity?

If it really is that high, I'd bring it down very slowly to about 35 ppt, which has sg ~ 1.0264.

I used to measure it with a hydrometer but got myself a refractometer. Both hydrometer and refractometer gives the same result.

Sparrow1617 · Jul 24, 2020

skimjim said:
Where are you collecting the NSW? From ankle deep water?

I don’t own a boat so pretty much yes. Well from where I can access the water. I don’t see how that influence my original question. The point I’m trying to make is that both fish and corals are visually doing better with the higher salinity water than with the lower salinity. Fish seems a lot less stressed in the higher salinity water, corals are opening up better.

Randy Holmes-Farley · Jul 25, 2020

Sparrow1617 said:
I don’t own a boat so pretty much yes. Well from where I can access the water. I don’t see how that influence my original question. The point I’m trying to make is that both fish and corals are visually doing better with the higher salinity water than with the lower salinity. Fish seems a lot less stressed in the higher salinity water, corals are opening up better.

It's likely the drop that bothers them, not the lower salinity.

Sparrow1617 · Jul 25, 2020

Randy Holmes-Farley said:
It's likely the drop that bothers them, not the lower salinity.

I think you hit the nail there. I will have to adjust the salinity very slowly.

Cory · Jul 25, 2020

Where is the salinity that high? It might be a testing error as salinity of the sea is usually 35 ppt or 1.026. Unless your from the red sea area at 1.029

Sparrow1617 · Jul 26, 2020

Cory said:
Where is the salinity that high? It might be a testing error as salinity of the sea is usually 35 ppt or 1.026. Unless your from the red sea area at 1.029

Haha no definitely not the red Sea area. I am from South Africa. Indian Ocean. Not sure why the salinity is so high. The guy at the LFS also confirmed that NSW in our area is too high to use just like that in an aquarium.

Reesj · Jul 26, 2020

I also used NSW for my water changes although I started out with mixing salt. Unfortunetly after coivd came there had been quite a lot of problems that made me unable to get water from ocean since march.

Anyway I went the other way of starting with hypo salinity at about 1.021 and got fish. Then when adding corals later I got mine up to 1.024 and now 1.026 which is my NSW salinity here. I have no clue if my refractor meter is correct as internet tells me that the salinity around Sri LAnka is about 1.024. But same as you I find the water I bring to be at 1.026, meaning higher.

I think your problem is getting them too low too quick . Also if you are keeping fish and corals from that area, your 1.029 might be alright. If not I would lower the salinity very slowly to about 1.027. You don't need 1.025. That is too low anyway for some one with your problem. Corals tend to do better at higher salinity while fish prefer lower. Also studies have shown that corals at higher salinity can withstand shocks such as temprature swings better.

Now what to do:
So if I were you, I would bring in the NSW and mix with rodi (or cleanest water you can find) and brind the salinity to 1.026. Then keep doing you water changes with those waters. Don't go and do 50% + water changes though

.
Once your tank gets to 1.026 salinity I will bring in NSW and mix them to be 1.027 and do the water changes fro mit till they stabilize near 1.0265-1.027.

Sparrow1617 · Jul 26, 2020

Reesj said:
I also used NSW for my water changes although I started out with mixing salt. Unfortunetly after coivd came there had been quite a lot of problems that made me unable to get water from ocean since march.

Anyway I went the other way of starting with hypo salinity at about 1.021 and got fish. Then when adding corals later I got mine up to 1.024 and now 1.026 which is my NSW salinity here. I have no clue if my refractor meter is correct as internet tells me that the salinity around Sri LAnka is about 1.024. But same as you I find the water I bring to be at 1.026, meaning higher.

I think your problem is getting them too low too quick . Also if you are keeping fish and corals from that area, your 1.029 might be alright. If not I would lower the salinity very slowly to about 1.027. You don't need 1.025. That is too low anyway for some one with your problem. Corals tend to do better at higher salinity while fish prefer lower. Also studies have shown that corals at higher salinity can withstand shocks such as temprature swings better.

Now what to do:
So if I were you, I would bring in the NSW and mix with rodi (or cleanest water you can find) and brind the salinity to 1.026. Then keep doing you water changes with those waters. Don't go and do 50% + water changes though .
Once your tank gets to 1.026 salinity I will bring in NSW and mix them to be 1.027 and do the water changes fro mit till they stabilize near 1.0265-1.027.

Thank you. That seems sensible.

Cory · Jul 26, 2020

Sparrow1617 said:
Haha no definitely not the red Sea area. I am from South Africa. Indian Ocean. Not sure why the salinity is so high. The guy at the LFS also confirmed that NSW in our area is too high to use just like that in an aquarium.

Ah okay. Well if it were me, I would use that nsw without changing a thing. Only problem is if you lfs has his down and you put fish in higher salinity it might shock them.