cleaning a BW tank?

[Mrs.Puff]

Im going to start my brackish tank soon(when i get my new hydrometer) and i was wondering how i would go about cleaning it after i have started the salt for a while. Lets say i take out 40-50% of the water, how should i go about adding more salt with the new, replaced water? Should i test the tank water first (with the hydometer) and than the new water (with the hydrometer also) and then see how much salt i should add in? Its a little confusing to me, but im sure its really simple. I tend to over-think things and then i just get myself all confused.

[LilGreenPuffer]

Just make your clean water match the salinity of what's in the tank.

Don't forget about freshwater topoffs every so often, too - when water evaporates, the salt stays, so over time your salinity may go up a bit. When that happens, just add a tiny bit of fresh water until it returns to the original salinity, letting it mix well before checking salinity. You can do this right before or after water changes, to keep things simple.

[Mrs.Puff]

ok...thanx

[bigfatpuffer]

I think i read it somewhere in the forum saying that if u want to raise the salinity slowly, general rule of thumb is the new water (if u r doing a 50% change) should be at a salinity at doubling it's desire salinity.

for example, your current salinity is 1.002 and u wanna raise it to 1.004. The salinity of the new water should be 1.008. So when u mix it will the 50% old water, that 1.008 will get diluted to 1.004.

correct me if i'm wrong. =)

[Mrs.Puff]

bigfatpuffer - that makes a lot of sense! Thats how i thought it should be

[Dadof4]

I think i read it somewhere in the forum saying that if u want to raise the salinity slowly, general rule of thumb is the new water (if u r doing a 50% change) should be at a salinity at doubling it's desire salinity.

for example, your current salinity is 1.002 and u wanna raise it to 1.004. The salinity of the new water should be 1.008. So when u mix it will the 50% old water, that 1.008 will get diluted to 1.004.

correct me if i'm wrong. =)

Actually this is not correct, that mix would take you to 1.005 and kill your biofilter. 1.002 + 1.008= 1.010. 1.010/2= 1.005. That can lead to huge errors as the SG gets higher.

Formula that can be used:
(X+Y)/2 = z

X=current SG
y= what you need to mix the new water to
z= desired SG

So if your current SG is 1.002, your desired SG is 1.004 you have:
(1.002+y)/2=1.004
I'm not going to show all the steps to solve this but...
(1.002+y)= 2.008
y=1.006

This is to figure out the mix for 50% water changes only.

[Mrs.Puff]

Now that what i call math! haha yea im going to have my fiance help me out with those formulas, im not good with those, even tho the ones you posted for me are pretty much the simplest formulas to work with. Thanx for your help

[Brent]

Math really is everywhere!

This reminds me of Algebra class. [Which I aced might I add] Haha

[Dadof4]

How long ago was that? I use algebra and trig all the time....

[LilGreenPuffer]

I think i read it somewhere in the forum saying that if u want to raise the salinity slowly, general rule of thumb is the new water (if u r doing a 50% change) should be at a salinity at doubling it's desire salinity.

for example, your current salinity is 1.002 and u wanna raise it to 1.004. The salinity of the new water should be 1.008. So when u mix it will the 50% old water, that 1.008 will get diluted to 1.004.

correct me if i'm wrong. =)

Formula that can be used:
(X+Y)/2 = z

X=current SG
y= what you need to mix the new water to
z= desired SG

So if your current SG is 1.002, your desired SG is 1.004 you have:
(1.002+y)/2=1.004
I'm not going to show all the steps to solve this but...
(1.002+y)= 2.008
y=1.006

I'm writing this down.