How many days can you keep RO water or mixed saltwater before it will start to cycle?

[basssnake]

Just wondering how long you can store RO water before it will begin a cycling process? Just wondering if anyone knows or has a opinion. Wouldn't be good to add ammonia or nitrates etc. to your tank for top off..... I have a air bubble stone in the RO water trash can.

Also, what about Saltwater made from your RO water.......how long before it will begin cycling and having ammonia, nitrates, etc.?? I made some saltwater yesterday (well had made 5 gallons on sunday and added enough salt to the same container so that i could add 10 more gallons of water yesterday). I plan to do the water change tomorrow night, so the premade saltwater will have sit for 2 days. I have a pump circulating the saltwater in the storage container.

Just wondering. I know i could test it, but thought i would get some answers on here for a long term idea of storing RO water.

I usually don't let premade saltwater sit around long. thanks for any comments/input.

[Shane Hoffman]

If you dont introduce an amonia source it will stay good until it evaporates. I keep mine covered (both RO and SW), its not uncommon at all for me to top off with water thats been in storage for 2 months. Ive never used water older than 3 months......I always double check nitrates and TDS before using and have never had a problem.

[dan3949]

RO water and saltwater can be stored for extended periods (weeks) with no problems. It is best to keep them covered and dark to prevent contamination and algea growth.

Stored water (RO or salt) cannot begin cycling unless there is a source of organic material to breakdown and start/feed the bacterial cycle. A covered/clean container will never generate ammonia/nitrite/nitrate unless an organics contaminate and start to decompose in the water.

[kato12]

How does Algae grow if there is no organic material and no bacterial cycle producing nitrates? What does it use as a food source?

[Dont Ask Me]

You can pretty much store it indefinately if kept out of the sun, and sealed well.

[floydie83]

You can pretty much store it indefinately if kept out of the sun, and sealed well.

+1 agreed. In a container with a cover out of the sun the water will keep for a long time

[deflux]

Agree - no sun, keep it closed up, and you can store it "forever"

[AC2020x]

Question, If I mix saltwater in a trashcan using a paddle. And then leave it stagnant, but covered, is that fine. Or do I need to keep the saltwater mixing with a pump?

Thanks!

[Silly clownfish]

Personally, I like to use water within a week. Yes, theoretically it will keep forever if sealed and dark, but that assumes you start with pretty sterile conditions. In reality, I don't do more than rinse my buckets between uses and sometimes I notice that the inside of the bucket feels slightly slimy. I assume that bacteria has been introduced from someplace: the air, my stirring spoon, my hands, etc. It doesn't take much for something to start to grow in a wet environment. Think of clean items you have put away at the end of the summer only to pull them out the following spring covered with mildew.

I wouldn't drink an unsealed bottle of water that had been sitting around for weeks, so I don't ask my fish to.

Maybe I'm over cautious, but I'd rather play it safe and make my water in smaller batches.

[Ron Reefman]

Question, If I mix saltwater in a trashcan using a paddle. And then leave it stagnant, but covered, is that fine. Or do I need to keep the saltwater mixing with a pump?

Thanks!

Left stagnant the oxygen levels will go down and other changes may start to take place that you don't want. Just drop in a pump and keep it stirred up some.

[dkeller_nc]

From the standpoint of "starting a cycle", the other posters on this thread are correct - RODI water, if pure in the first place, won't develop significant amounts of nitrates even if stored for weeks/months.

However, this isn't the same as saying that RODI water will remain sterile. Biofilms can and will develop even in highly purified water, and is a major issue in my industry (medical/pharmaceutical manufacturing). That's why even really, really expensive and highly sophisticated water purification systems incorporate sterilizing UV radiation in a circulating pure water loop, why it's kept circulating, and why the whole system must occasionally be taken down and sterilized with (typically) peroxyacetic acid.

Would it still be good for a reef tank? Sure - our tanks are jam packed with bacteria, and the small amount that might be introduced by "old" RODI water is pretty insignificant.

As to saltwater, this is a bit different. Seawater is very, very complex from a chemical standpoint, and as Ron points out, allowing it to go anoxic can result in significant chemistry changes. Moreover, there will be a small amount of nitrogen in virtually ever sea salt, no matter how "pure". And so it will support microbial growth. However, in my opinion artificial seawater is good to go for a reef tank for at least a month if it's in the dark, and kept circulating (oxygenated) and at approximately the right temperature.

I would not, however, recommend using an airstone to keep ASW circulating for long periods of time. There are several reasons for this, but one of the big ones is that it will evaporate and concentrate. If that's kept in check by regular additions of RODI, then there's no issue. But you don't want ASW concentrating past perhaps 1.030 specific gravity, as you may exceed the solubility limit of some of the elements in the mix, and once precipitated, they can't easily be redissolved (calcium precipitating as calcium carbonate is an example).