Kati Ani


I was reading online and came upon something I never heard of so I'll ask you guys. What's up with a kati ani water system? Are they any good? worth the money? dangerous for me or my reef? more expensive then ro/di? The things I read about them there faster then ro/di and don't use prefilters or carbon. They produce 16 gal. an hour. Thewy don't sound to bad please let me know am I missing something that makes them bad? The last thing I want is to waste more money!


Premium Member
Got a link to the one you're considering?

In general, kati-ani is just a separation of the DI resin stage of a standard RO/DI filter into its separate components. This separation makes it easier to recharge the resin so it can be used repeatedly.

In some systems utilizing kati-ani resin, the RO membrane is left out and the volume of resin is greatly increased, so instead of relying on the membrane to remove most of the remaining ions, you rely solely on the resin. Generally, carbon and a sediment filter are still used prior to your resins. By removing the RO membrane and relying on the resins, you eliminate waste water which is why the output of this type of filter is so much greater than a standard RO/DI unit.


Premium Member
I can't say for sure, but it looks like the "this may not work for everyone" points they are raising are for people who might use them on the tank itself. If you're using it for filtering tap water I wouldn't expect any problems from it.

To me, it sounds like you save a little money in water bills and in replacement cartridges, but you lose a little time doing the regen.

I think most people would still benefit from using carbon and sediment filters prior to the resin as it would just make the resin last longer.


New member
The chemicals to regenerate the resins are cheap, you just have to be careful. The Filterguys were going to put together a regen kit to simplify things. Your tap water quality will determine how often you will need to regenerate. Where I live it would be too often so I will stay with my Filterguys six stage RO/DI.


New member
I have a similar unit, however it is made by Kent (the 200R - R stands for rechargeable). It includes a carbon pre-filter a separate cation and anion resin. I cannot comment on how good it is long-term as I only used to fill my 20L a couple of times to get my plecos to breed, right now it isn't in use but if you're comfortable with handling HCl and NaOH (cheap to obtain) it shouldn't be too difficult to recharge. The sole reason I got it was it produces no waste water and it produces purified water on the turn of the valve. I would say it is cheaper to run than an RO unit, but maybe not practical if you have really hard water that has a TDS of over 350 ppm.

Roland Jacques

Premium Member
If you only need a very little bit of pure water than DI only may work for ok for your reef. DI only does not last very long

Do you mind handling and deposing of the regen chemicals.

my question is If you regen your DI is the water quality get worse than a disposable Mixed bed DI?

PS. you DO need a good carbon prefilter before your DI. if I was going to use DI only I'd use the best prefilters I could find. A .2 micron mechanical Zeta Zorb and a .5micron chorine guzzler at least.

Artisan Corals

In Memoriam
I would like to answer some of the previous Kati Ani questions.

Kati Ani is produced in Germany and does not need any prefilters to achieve 99% water purity. Of course you can use prefilters and they may extend the time between regenerations, but the regenerations are so cheap that the prefilters cost more in the long run.

The resins can be regenerated over and over again for decades. The regeneration process takes about an hour and uses common (but dangerous) chemicals.

Very high TDS water will use up the resin faster than low TDS. However, this same high TDS decreases the efficiency of an RO system and requires quicker replacements. You can purchase several sizes of Kati Ani to account for differing water hardness and the amount of water processed.

Considering the throughput is 385 gallons per day, the initial cost is similar to an RO system and the ongoing cost per gallon to purify water is much cheaper than RO systems. I've worked with several larger aquacultural facilities that replaced their RO systems after a cost analysis compared to Kati Ani.



Premium Member

Is it possible to install a Kati Ani unit with an auto shut off that is similar to how my current ro/di system tops off my reservoir?


Artisan Corals

In Memoriam
The Kati Ani can not be used under pressure, so the auto shut off must be plumbed before the Kati Ani unit. But yes, the Kati Ani can be used in this automated manner.


Premium Member
I have in the past considered adding a chamber and running the 2 part DI after the prefilters and RO membrane. Problem is, it is pretty hard to find the seperate parts of the resin. Filterguys has the anion portion, but not the cation for sell. This would keep your unit working the same as before, but it would be less costly for resin recharges. There was a thread on here a while back on recharging your resin, but you need to seperate the anions and cations to do so. That would not be fun and would take a while.