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water change questions

Jun 25, 2004
if i have a 50 gallon tank, how often should i do a water change and how much should i take out. Then when i refill it, should i purify tap water and put synthetic sea salt in it until the salinity is ok?
any help is awesome!
I use RO water every 2 weeks and do 15 gallons each time. Some stores sell RO water from a machine for $.50 a gallon. Then I mix it with salt in a large rubbermaid bin with a pump and venturi valve to aerate it. Usually I start mixing it in the evening then go to bed and do the water change in the morning. Be sure to check the water's ph and salinity before the change though.
At one time we had a lot of people reporting in where this could be found and it was widely available. I think even Walmart (or was it Target) was a source, and Culligan (which sells drinking water) also carried it. Many upscale grocery stores will have it.

You might have to look a little harder for RO/DI water, but I found it not only in the local LFSs, but at the Whole Foods Market (they had an RO/DI water dispenser, and you could choose either RO or RO/DI).

I've found it very convenient to use salt buckets for water mixing and changes - they actually hold about 7 gallons.

Hm, here's a question from me too:

Does it absolutely HAVE to be RO/DI water, or is RO water alone ok too?
I know they sell RO water kits here (still have to find a shop that sells ready to use RO/DI water), but about the DeIonizing (that's what it is right?) I have no clue at the moment :?
Kent Marine and many other companies make RO/DI units suitable for producing water usable in aquariums.

Some people do use RO water only and that's what some LFSs use, but the larger ones sell RO/DI water here.

Dont forget to alter the temp of your RO/DI water to your tank temp before you make it up as this will affect the salinity!

Check the tank salinity too before addind it... if you constantly add water that is about 36ppt to a tank and never check the tank you will be surprised how quickly it shoots up with evaporation!

To say that you have to use RO/DI water is slightly excessive.

I use natural Sea water for all my tanks, they keep seahorses, jellyfish, octos, sharks and sea snakes fine and dandy! But make sure your local sea water is clean... I do have to filter the Iron out of mine!
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