Rodi filter question for hard core sps keepers?

[MattL22]

Just wondering for the hard core sps tanks out there in the 2-300 gallon range how often do u change ur filters and DI resin

I've always done it when tds hit 2 but I just can't seem to get po4 down I'm contemplating running a Gfo reactor in my new salt I make 40-50 gallons a week fresh salt and about 15-20 for top off so I'm making 70 gallons a week give or take so should I be changing them more often

 

[choff]

I run dual DI so I can totally exhausted the first cartridge. I never let my TDs reach 1

 

[MattL22]

Bump

 

[MattL22]

Btw I have 5 stage air water ice typhoon with 50 gpd membrane

 

[AZDesertRat]

I run the MaxCap UHE-100 and change the MaxCap DI cartridge at 1 and the SlicaBuster DI cartridge after 3 MaxCap replacements at which time it is starting to creep up to 1 TDS. The MaxCap lasts about a year and the SilicaBusters about 3 years with a 100G mixed reef w/30G sump and a 16G nano.Around 1100-1200 gallons per MaxCap and 3500+/-out of the SilicaBuster.
Previously I had a Typhoon III and could not get more than 150 gallons out of a DI no matter what I tried so sold the system and bought my first MaxCap, which turned into a dual membrane 180 GPD MaxCap which was later replaced by a MaxCap UHE-100. Never looked back.

 

[tigerdragon]

Changing the filters depends on your supply water and how dirty it is. Di resin i change when it hits 1 on the tds meter. I have a tds meter setup that monitors incoming water, output of ro membrane and output of di resin.

 

[Randy Holmes-Farley Verified Community Expert]

I would replace the DI when it hits 1 ppm TDS, but you can always measure phosphate in the DI water if that still concerns you.

FWIW, unless it is pretty high (well above 0.1 ppm), it isn't a big source relative to foods.

I show that here:

Aquarium Chemistry: Phosphate And Math: Yes You Need To Understand Both ? Advanced Aquarist | Aquarist Magazine and Blog

from it:

Comparison of Food Sources of Phosphate to Other Sources
What about other sources of phosphate, like the "crappy" RO/DI water containing 0.05 ppm phosphate? A similar analysis will show it equally unimportant relative to foods.


Let's assume that the aquarist in question adds 1% of the total tank volume each day with RO/DI to replace evaporation. Simple math shows that the 0.05 ppm in the RO/DI becomes 0.0005 ppm added each day to the phosphate concentration in the aquarium. That dilution step is critical, taking a scary number like 0.05 ppm down to an almost meaningless 0.0005 ppm daily addition. Since that 0.0005 ppm is 40-600 times lower than the amount added each day in foods (Table 4), it does not seem worthy of the angst many aquarists put on such measurements. That said, tap water could have as much as 5 ppm phosphate, and that value could then become a dominating source of phosphate and would be quite problematic. Purifying tap water is important for this and many other reasons.

 

[AZDesertRat]

What are your tap water and RO only TDS readings? Do you know if your water utility feeds phosphates for corrosion control in the water distribution system?

I can tell you from experience, NY waters are hard on sediment and carbon block filters. While most has low TDS, the TSS or suspended solids content is quite high and plugs the sediment filter and fouls the carbon. Spectrapure researched this several years ago and developed their 0.2 micron ZetaZorb for that reason. They did a bunch of long term real world testing with users in the NYC area and found the pleated ZetaZorb with its 10x surface area over a regular spun poly filter lasts many times longer, filtered much better and it has lower headloss. It can also be carefully rinsed and cleaned a few times before it is shot so ends up being a bargain even with its higher initial cost since it will outlast several normal filters. By doing this you protect the carbon blocks billions of tiny microscopic pores better so it also lasts longer, functions better and does a better job of protecting the RO membrane so it also performs better and lasts longer which in turn makes the DI last longer.

 

[MattL22]

Thanks for the info AZ I'll look into that filter!

Tiger dragon I'm getting a 0 tds reading right now from my unit but I still fight po4

Randy thank you I've read ur article and I've cut feedings back to every other day to see about not adding more po4 then I'm exporting I'm using Gfo I was using lanthaium chloride but decided to stop using it as sps didn't seem to like it and skimmer would go crazy couldn't dial it in!

I hate to cut back feedings even more I have 20 or so fish I'm my 220 and don't like to under feed would every 3 days feeding be too little