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Question About RO Water


Jan 12, 2007
Although I do not own an Octopus yet, I hope to learn a lot from this site and hopefully own an Octopus in the future... But there has been a question on my mind for some time now, and I think the best way for me to come to a decision is to ask for advise and other opinions

Regarding the use of Reverse Osmosis water, I am wondering if it will be worth while to BUY a RO filter for home use? And if so do they HAVE to be hooked up straight to your tank, or can you just filter water and save for future use? Or is it better to buy RO/DI water from the store? Does anyone own their own filter?

I have a 90 gallon tank and I am planning on using a Sump as well as an additional back up reservoir with an auto top off controller. And from what I understand it's really important to use RO or RO/DI water?... Also, is it better to get a Protein Skimmer that is overkill for a 90 gallon? I would really appreciate some advise. I am terrible with making up my mind! Thank a lot.
It is important to use RO water for topping off your tank after evaporation and mixing your own saltwater for water changes. It doesn't contain any undesireable elements that could be detrimental to your livestock.

I don't own an RO filter system, but I sure wish I did. It would save time and money in the long run, between trips to the store and the cost of buying over and over, not to mention hauling jugs or buckets of water back and forth.

I've read that it's actually bad for a tank to over-skim the water. I'd personally suggest a quality skimmer that's rated for your tanks size, to the additional filtration, which you may have already read, should be rated for 3 times the size of your tank.
I wouldn't worry about overskimming the tank--that's mostly a problem for reefs. Skimmer (and all aquarium accessory) manufacturers exaggerate their products' capactiy quite a bit. A skimmer that advertises itself as suitable for a 90 gallon tank generally isn't by a long shot. Look for products claiming the 150-250 gallon range.

RO/DI water is necessary for a healthy system, its entirely up to you whether you get it from the store and lug it in buckets or set up your own filter. I suspect you'll find that on a 90 gallon tank the latter is a better option. You'll also practice better husbandry since you'll do more water changes if you have the water there in your house.

RO is key in a healthy tank, especially with saltwater evaporation. with 90 gallons, you'll be doing pretty large water changes, and it will save you a lot of time and money in the long run.

I already had a filtration system set up in my home when I moved in, but I have heard of people having issues installing RO systems in their home if the plumbing won't support it - this seems to especially be an issue for renters....so hopefully you own your own home!

Thanks a million for the feedback! This information has helped me alot! I want to be thorough and careful so I can create the best possible envirionment I can.
I have a small RO/DI filter that I set up in a sink in my basement. It can filter about two gallons in an hour or so - but I usually just let it drip into a 5 gallon bucket while I am doing other things around the house - and then make my seawater. The only problem is when I forget - but luckily it is near a floor drain!!!
Owning your own RO/DI unit is definitely the way to go if you have a place to keep it hooked up. The tap on is simple. Cuttlegirl, you can get a very inexpensive and easily attached float valve that will let you leave it on all the time without overflow (until you block the float with a cord that is ;>). I keep a 20 gallon bucket mixing bucket and a 20 gallon holding tank in addition to the enclosed 3 gallon (actually only provides 2 gallons of water) that you can get with any system.

If you have a garage/basement/laundry sink available, this is ideal. There are overly expensive units that are designed to fit under a kitchen sink to provide drinking water (RO only - DI water is not potable) but if you are willing to invest a little DIY effort and have room under any sink, there are several on eBay that are considerably cheaper and can still be mounted under a sink (mine is designed to be able to get just RO for drinking - or testing - in addition to RO/DI for the fish tanks). Apartment dwellers have some problem though because it is most desirable to tap both the COLD water supply and the drain to keep an invisible setup (I actually leave my drain line open to the sink but it is in a garage area that we built out for the fish stuff). If anyone is interested in setting up a home unit and would like a detailed setup description, let me know and I would be happy to photograph and explain what we have done.

One caveat, as cuttlegirl noted, the units for the home, small or not, only produce between 1 and 2 gallons an hour (regardless of what the ads say since pressure is the primary factor in gpd and homes are regulated at about 60 PSI). Additionally, for every gallon produced between 1 and 4 gallons will be created as run off and need an exhaust drain.

An additional caveat that should be noted is a warning that owning your own RO/DI unit does not make the water "free". The filters need regular changing and the RO filter is quite expensive. Changing the particulate filter regularly and back draining (if your unit has the capability) the unit monthly will extend the life of the RO filter. The DI sand will also need replacing as it separates and ages. Buying the particulate filters in bulk significantly reduces the cost.
dwhatley;86080 said:
If anyone is interested in setting up a home unit and would like a detailed setup description, let me know and I would be happy to photograph and explain what we have done.

I'd definately like to see some photos. I'd be interested in learning more about about RO/DI systems. Does Tonmo have a Wiki? Seems like it would be a great place for this. (let me know if help is needed in this area, I've set up a few)

I bought a 6 stage RO/DI filter from eBay about 2 years back when I started saltwater tanks. It was a 100 gallon per day system, which made maybe 10 gallons per day.

Since then its been moved, my filters needed to be changed, I couldn't find exact matches, etc. I'd be interested in learning how the RO system should be set up, ie, how each stage should be set up (filters (micron size?), charcoal, DI, etc).

I've since changed my plumbing around, and I have a utility sink, but the RO/DI unit is in a few pieces with a few random filters. I'd like to learn how to set it up properly, get new filters, a few spare parts (the lid to one of my filters cracked) and get this set up for good.

Thanks in advance!

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