Salt water (red sea mix)

[reefin-rofin jr]

Hello,
I am a newbie..........
I am currently making my first (water change) for my 75 gallon tank. I have a 37 gallon brute rubbermaid container. I was told to make a 20% (15 gallon) water change every 4-6 weeks. Well I just made my RO/DI water and am about to add the salt to i and to let it sit for a day or so. I do not have a scale and it says to add 1.4 Lbs per 5 gallons so I need to add 4.2 lbs of salt. Can anyone give me a rough estimate as to how much that is? I am going to just add about 3 cup fulls and let it sit. I have a heater and power head for circulation. Hopefully tommorrow the specific gravity is 1.021ish. Then add the water to tank?

Is this a good and convient way to do the water changes?(I am looking for the easiest).
Do I even need the powerhead for circulation? (since it will be sitting for only about a day or so.)
Is about "from a measuring cup" 3 cups .......4.2 pounds of salt.

Thank you for the advice...........I LOVE THIS FORUM

P.S.
For future changes can I make the water like 3 weeks ahead of time and let it circulate and still be safe?

[46FiatYamaha]

http://reefkeeping.com/issues/2007-03/rhf/index.php A lot of good info on mixing salt. Usually it takes me around 13 cups of salt to get a specific gravity of 1.026 in 15 gallons, you should use a hydrometer or better a refractometer for measuring the salt level, just dry weight alone won't be accurate enough. You should keep a powerhead and heater in it all the time to keep it aerated and the correct temperature. http://reefkeeping.com/issues/2007-11/nftt/index.php also good info on water changes

[kraze3]

Yes you need a powerhead to keep the water mixing. This will make sure all the salt is disolved and mixed evenly. You will also need a heater to get the new saltwater the same temp as the tank water.
I use different salt so cannot help but I would try a little less than what the bucket says then work your way using your refractometer. I would also try to bring your sg up a little. I keep mine at 1.026.
When I do my changes I siphon water out into 5 gallon buckets. I then pump my water back in through my sump. I would stick to doing 10% water changes weekly or 20% bi-weekly. 4-6 weeks is too long in between in my opinion.
You can mix up your saltwater in advance but its best to keep it in a covered container and mixing. You can stop the powerhead and then plug it back in a day or 2 before the change.

[Felix T Cat]

I have found the Red sea mix is about 1/2 cup salt per gallon of water. Definitely double check with a ref or hydro.

[reefin-rofin jr]

Thank you for all of the information.
I just added about 7 cups of salt to the 15 gallons of water.
I will let it sit for a day and then recheck the specific gravity with a hydrometer. I now hear it is best at a level of 1.026.

I have the powerhead and heater running as we speak.
So It is "wait and see" till tommorow.

Hopefully I will not be far off so I wont have to worry about adding more salt or more water.............
This is great, So for next time I will be able to use this water change as a future guide for the following water changes.......it just gets easier.............

Thank you for all the information......ill keep everyone posted.

[PRDubois]

My guess is you will need 1 more cup of salt but let it mix and then use refractometer. You can buy one online for $40

Until you get a refractometer, get someone to calibrate your Hydro with a refractometer. My Hydro is 0.003 high

I also do 10% every week and mix to be 1.025