Water Changes. Which Volume Do I use?

N

nano_thomas

This may be a silly question, but do I do the water change based on the total volume of the tank or just a % based on how much water is actually in the tank?

I have a 29g BC and when I originally put the 30# of arg in there it only held just over 20g of water. Now I have around 38# of LR so I'm guessing I only have about what? maybe 15-18g of actual water?
 
In general, 15-20% water change of total water volume, once a month. I have a 29g with 10lbs. of sand and 20+ lbs. of LR and do a 5g water change once a month.

Mark
 
Hi,

Here a calculator to help you figure out your total volume based on dimensions, amount o f LR/LS etc. http://tinyurl.com/yaoruo . HTH

Cheers,
 
He brings up a good question.


Change your water as a function of your total system volume, not just of your display. So if you have a 120G, don't do a 10% water change of 12 gallons.

Count the estimated volume of your sump too, as if it was one big tank.

So in my case, I have approx. 24G in my sump. so if I was to do a 10% change I do three jugs (or 15G)/


Just my .02.


Brad
 
My thoughts as well...

Don't let anyone tell you how often to do a water change. Some people do a smaller one more often and some people do a larger one less often. You will learn to "see" how things are doing in the tank and will get a feel for how often you need to do one base on your bio load, feeding habits, filtration/skimming etc.

Personally I would start by doing one weekly or bi-weekly until you feel comfortable with how things should look and then you can extend the time between the changes. You will learn what is acceptable quickly enough. IMHO
 
Also to be noted is that some folks go by Nitrate levels to determine how frequently to do water changes.


Just keep in mind that salt mixtures have more than salt in them, they have trace elements like Magnesium, etc. Keep in mind that you're not only taking bad stuff out, but putting good stuff back in when doing water changes.

I personally do a 10% water change every 3 weeks. This will increase to bi weekly once my bio-load increases.

Take a look at this analysis and see if you can see why you'd need to do regular water changes, in spite of whatever your water is testing at for the Big 3 (Calc, Alk, and Mag)

http://www.advancedaquarist.com/issues/sept2004/feature.htm

Brad
 
Ok so I shouldn't do the water change based solely on volume alone. I've been doing weekly water changes at around 4g per week.
 
One calculator I found online mentioned using 60-70% of display volume + 50-60% of sump volume as the basis for figuring our how much to change, since live rock, corals, sand, etc take up volume.
 
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