Salinity Question/Calculator

flounder · Nov 23, 2014

I am thinking about starting a rotifer culture. Which is suppose to be harvested daily. That culture will be at 1.018, and my tank is 1.026.
My culture should have me adding/harvesting a half gallon daily. If I add a half a gallon of 1.018 to 1.026....how do I figure out if I am going to mess anything up.
Tank stats:
I do 50 gallon water changes every 2 weeks.
Total volume is about 300g.

So with 1/2 gallon daily, 14 days....I will be adding 7 gallons of 1.018. This added water will also mess up my ATO though, as it would not top off as much, or at least a half gallon less freshwater each day. So after 2 weeks I'd really be up 7 gallons of 1.018 AND down 7 gallons of fresh.
Or at 300g it isn't going to make a difference.

*I do know that I could use a strainer and pour my culture through that, and just use that in my tank, but I think adding rotifers with their water would be easier to do. (and lazier)

Thanks,

Reefing Madness · Nov 24, 2014

Randy Holmes-Farley · Nov 24, 2014

Assuming the total water volume is 300 gallons, the change to salinity is trivially small.

1/2 gallon of sg = 1.018 added to 300 gallons of sg = 1.026 --> (0.5 x 18 + 300*26)/300.5 = 1.02599 :)

Since most people correct for water volume by topping off with fresh water, this addition will very slowly actually raise the salinity since a portion of the evaporation replacement is not pure water but the 1.018 water (assuming it is an addition and not a swap for tank water).

It is not enough to worry about, but you can always do an addition every third time and a swap the other two times and you'd be just about perfect. :)