Salinity change question

[PeterEde]

Away 2 days left friend to feed fish.
I asked to check water level after hot day.
Says pump making noise.
I ask to add 2litres to top up.
Tank is 120 lt minus sand rock maybe 100 lt.
Salinity was 35. Friend added 4 litres.
Will this drop harm the fish.

 

[Surfandturf]

Away 2 days left friend to feed fish.
I asked to check water level after hot day.
Says pump making noise.
I ask to add 2litres to top up.
Tank is 120 lt minus sand rock maybe 100 lt.
Salinity was 35. Friend added 4 litres.
Will this drop harm the fish.

So for me, I use gallons. Looks like you have an actual water volume of 26 gallons (100 liters) . I also use specific gravity and converting your 35 ppt gives you 1.026 which is what I run my reefs at. Now assuming that your friend added one gallon of water (4 liters), I would say that you should be fine. The only concern I would have would be the pump and how long it was pushing air rather than water or a larger mixture of air/water. Honestly that would not hurt the fish. Did the temp drop? I would be more concerned with this aspect.

 

[PeterEde]

So for me, I use gallons. Looks like you have an actual water volume of 26 gallons (100 liters) . I also use specific gravity and converting your 35 ppt gives you 1.026 which is what I run my reefs at. Now assuming that your friend added one gallon of water (4 liters), I would say that you should be fine. The only concern I would have would be the pump and how long it was pushing air rather than water or a larger mixture of air/water. Honestly that would not hurt the fish. Did the temp drop? I would be more concerned with this aspect.

It's been a hot day. The water jug (approx 1 gl) would have been warm.
I am running an evaporation fan over the tank.

Sounds like just a misunderstanding of how much water was I the return section.
Should be ok for a few days.
Seems I now know I need an ato for longer times away.

Thanks

 

[Randy Holmes-Farley Verified Community Expert]

Away 2 days left friend to feed fish.
I asked to check water level after hot day.
Says pump making noise.
I ask to add 2litres to top up.
Tank is 120 lt minus sand rock maybe 100 lt.
Salinity was 35. Friend added 4 litres.
Will this drop harm the fish.

No. It's a very small salinity change.