Is an RODI water filter really necessary?

DrFlu · Oct 19, 2021

Hello everyone,

I have been reefing with mostly LPS/Softies for the last >10 years and recently gotten some SPS within the last few months. However, i have not been following one of the most basic principles in reef keeping: NOT using RODI water. I have been using tap water with Prime this whole time.

I have to say though, I have not been experiencing any issues as others have reported? I have not been getting cyano, dinos etc. Corals seem fine? I run a Chaeto reactor 24/7 and also a HOG1x algae scrubber. I also run GAC every few months - so that may that probably solves any heavy metals accumulation?

Nitrates: 1ppm (salifert)
Phosphates: 0.03ppm (salifert)

Am i missing something here? Is a RODI unit for reef tanks really a fundamental piece of equipment? I just couldn't justify the purchase of an piece of equipment that is seemingly not required.

jrill · Oct 19, 2021

It depends on the quality of your tap water. There are folks who don't need one. Apparently you are one of them.

kittenbritches · Oct 19, 2021

How much have you spent on Prime over the last decade? My RODI unit was $60. It has more than paid for itself IMO.

mdb_talon · Oct 19, 2021

For me it is certainly required equipment. I dont want to risk something in my water causing issues. My water is horrible, but even if it was not who knows when that changes and for what i consider a relatively minor cost i dont want to risk it.

Having said that there are plenty of people who can chime in about using tapwater and never having issues. I am sure i cant change their mind that it is fine and they certainly cant change mine.

Perthegallon · Oct 19, 2021

I feel like one containment in the drinking water could kill thousands of dollars worth in your tank I feel it’s as important as having a back up on your heater. Just my two cents and the machine cost basically nothing so why not

jskidds2294 · Oct 19, 2021

DrFlu said:
Hello everyone,

I have been reefing with mostly LPS/Softies for the last >10 years and recently gotten some SPS within the last few months. However, i have not been following one of the most basic principles in reef keeping: NOT using RODI water. I have been using tap water with Prime this whole time.

I have to say though, I have not been experiencing any issues as others have reported? I have not been getting cyano, dinos etc. Corals seem fine? I run a Chaeto reactor 24/7 and also a HOG1x algae scrubber. I also run GAC every few months - so that may that probably solves any heavy metals accumulation?

Nitrates: 1ppm (salifert)
Phosphates: 0.03ppm (salifert)

Am i missing something here? Is a RODI unit for reef tanks really a fundamental piece of equipment? I just couldn't justify the purchase of an piece of equipment that is seemingly not required.

Considering the cost of dechlorinator vs RODI filter media that alone makes it worth it for me. Dechlorinator even if you buy it in bulk is still more expensive then the resins bought in bulk. Plus if you keep a large reserve of Rodi water made in a brute can or two, you are just as ready to go as if you used tap.

CanuckReefer · Oct 19, 2021

kittenbritches said:
How much have you spent on Prime over the last decade? My RODI unit was $60. It has more than paid for itself IMO.

This true. Although you must pay to renew filters in it occasionally? Still likely far less than dosing Prime.
I purchase mine from my local retailer for 3 bucks a large jug bi-weekly on a 90 gallon fwiw... my tap water is so hard it would kill the tank in likely seconds lol.

kittenbritches · Oct 19, 2021

CanuckReefer said:
This true. Although you must pay to renew filters in it occasionally? Still likely far less than dosing Prime.
I purchase mine from my local retailer for 3 bucks a large jug bi-weekly on a 90 gallon fwiw... my tap water is so hard it would kill the tank in likely seconds lol.

The carbon cartridge needs to be replaced every 1500 gallons of water filtered, and the sediment cartridge can last upwards of two years. Replacing the carbon, sediment, and DI cartridges is about $30 total, and I don't have to lug jugs or buckets around.

CanuckReefer · Oct 19, 2021

kittenbritches said:
The carbon cartridge needs to be replaced every 1500 gallons of water filtered, and the sediment cartridge can last upwards of two years. Replacing the carbon, sediment, and DI cartridges is about $30 total, and I don't have to lug jugs or buckets around.

Hey! It keeps me fit!

kittenbritches · Oct 19, 2021

CanuckReefer said:
Hey! It keeps me fit!

I can't argue with that!

DrFlu · Oct 19, 2021

From where I am from, an RODI unit costs ~$200-300 AUD for the most basic 4-stage unit and replacement filter cartridges costs $100 AUD. You guys are lucky to have access to cheaper high quality equipment. I only spent $50 AUD a few years on prime (1L bottle can treat 40 000L of tap water), I have a 200L tank (10% water change per week = 1040L per year). My tap water is around 2-3dkH

In theory 1 x 1L bottle can possibly last 40 years if measured out with complete accuracy. I am still at a loss?

Gtinnel · Oct 19, 2021

kittenbritches said:
The carbon cartridge needs to be replaced every 1500 gallons of water filtered, and the sediment cartridge can last upwards of two years. Replacing the carbon, sediment, and DI cartridges is about $30 total, and I don't have to lug jugs or buckets around.

How are you getting 2 years from a sediment filter? The membrane often last around 2 years but I replace my carbon and sediment several times a year.

kittenbritches · Oct 19, 2021

Gtinnel said:
How are you getting 2 years from a sediment filter? The membrane often last around 2 years but I replace my carbon and sediment several times a year.

"Can last."

I'm still a new kid and only bought mine in August.

CanuckReefer · Oct 19, 2021

DrFlu said:
From where I am from, an RODI unit costs ~$200-300 AUD for the most basic 4-stage unit and replacement filter cartridges costs $100 AUD. You guys are lucky to have access to cheaper high quality equipment. I only spent $50 AUD a few years on prime (1L bottle can treat 40 000L of tap water), I have a 200L tank (10% water change per week = 1040L per year). My tap water is around 2-3dkH

Wow. Ours here in Canada not as cheap as US. Probably 150-200 for a basic unit....cartridges would be about 75 . This when I last priced it a few years back. Probably more though now with supply issues worldwide. Thus I lug my bottles....its a nice journey when I need to escape the house. 'OK Gotta go get some water! C ya! '

zheka757 · Oct 19, 2021

Is it necessary? Probably not for everyone. I'm not on city water. and my water comes out from ground at 900-1200tdc, stinky, discolored water, here in florida. Then I have whole house RO system and from that stinky water I get it down to 70-80tdc. And then I have a second RO for just my aquarium, and I get it down to 2-4tdc. Not using DI filter.
Not all the minerals are bad in tap water. Some people know whats in their tap water, and use filter to strip only harmful minerals out of water. Putting the rest in their reef tanks.

Gtinnel · Oct 19, 2021

kittenbritches said:
"Can last." I'm still a new kid and only bought mine in August.

I believe it's typical to replace the sediment and carbon at the same time. I do it after I see any pressure drop before the membrane or I'll do it when the sediment filter looks disgusting. Which for me is usually every 6 months or so. The membrane I replace when the permeate tds rises to 3ppm, which for me is about 97% rejection rate. That has me replacing the membrane about every 2 years.

I honestly just assumed you meant membrane and just said the wrong one. If anyone is getting 2 years from their sediment filter they either have incredibly clean water, or they're not filtering very much water.

N.Sreefer · Oct 19, 2021

My city water is only 2ppm but part of that impurity is copper which started to build up over time in my tank causing coral recession. Now I feel like an rodi is more than worth the investment for peace of mind.

CanuckReefer · Oct 19, 2021

N.Sreefer said:
My city water is only 2ppm but part of that impurity is copper which started to build up over time in my tank causing coral recession. Now I feel like an rodi is more than worth the investment for peace of mind.

Wow, 2ppm is really good.... I need some of that NS water. As you mention, the copper though....anything but the copper, you'd probably be ok. Darn.

Gtinnel · Oct 19, 2021

CanuckReefer said:
Wow. Ours here in Canada not as cheap as US. Probably 150-200 for a basic unit....cartridges would be about 75 . This when I last priced it a few years back. Probably more though now with supply issues worldwide. Thus I lug my bottles....its a nice journey when I need to escape the house. 'OK Gotta go get some water! C ya! '

I'm in the US and can't buy a rodi filter for $60. The cheapest I see them is for is closer to $200. I'm going to guess that @kittenbritches may have got hers from the marine depot closeout or if not just found a phenomenal deal somewhere. I don't need another rodi but for $60 I would've bought several spares, it's worth that just for the membrane and cartidges.

N.Sreefer · Oct 19, 2021

CanuckReefer said:
Wow, 2ppm is really good.... I need some of that NS water. As you mention, the copper though....anything but the copper, you'd probably be ok. Darn.

I was really surprised when I tested it must've checked it 20 times then I decided I didn't need an rodi which wound up being a mistake, darn copper. Might be from the old plumbing in my house. I actually miss my well at my old place in lawrencetown 2ppm water tastes gross.