Water changes. . . . What is your method?

[VintageReefer]

What is cac?

Catalytic carbon. Supposed to be better and not remove trace somehow

 

[VintageReefer]

The video mentions a supplier but they only sell in large quantities for like…150$ I forget exactly how much.

You can get it by the 1/2lb or lb here for much less

https://www.corallife.us/product/catalytic-activated-carbon

 

[Randy Holmes-Farley Verified Community Expert]

Is cac any better?

I don't know if it is better or worse, but I would not assume it can bind very hydrophilic toxins. I'm not suggesting folks look for it or be concerned about it in particular, but a toxin like monofluoroacetate will not appreciably bind to gac (or anything else I can think of) from seawater. :)

 

[Randy Holmes-Farley Verified Community Expert]

Catalytic carbon. Supposed to be better and not remove trace somehow

Does that sound plausible to you, Christoph (an expert chemist who has actually measured trace binding to GAC)?

@Christoph

 

[VintageReefer]

Does that sound plausible to you, Christoph (an expert chemist who has actually measured trace binding to GAC)?

@Christoph

To me it does not. But this is not the first I’ve heard the claim. I have not dig deep into cac research or how it differs from other carbon, and I have zero experience with it.

I only learned about it a few weeks ago, did some mild reading, and decided I want to learn more about it and peoples experience with it

 

[VintageReefer]

I despise AI but here is what chatgpt says about gac vs cac

I don’t know how true this is

GAC vs. CAC: What’s the Difference?​

Feature	GAC (Granular Activated Carbon)	CAC (Catalytic Activated Carbon)
Primary Use	General organic removal	Removes chloramine, hydrogen sulfide, and ammonia more effectively
Surface Chemistry	Standard activated carbon	Chemically modified (usually with iron or manganese) to enhance reactivity
Structure	Microporous or mesoporous	Similar structure, but chemically more reactive
Common in	Reef tanks, aquariums, water polishing	Water treatment (especially chloramine-heavy water), specialized aquaria

---

Benefits of Catalytic Activated Carbon in Reef Tanks​

1. Superior Chloramine Removal
   • If you’re on city water treated with chloramines (a mix of chlorine + ammonia), CAC can break them down much more effectively than GAC.
   • Helpful if you make your own RO/DI water and your carbon block isn't fully removing chloramines.
2. More Reactive Surface
   • It can break down more stubborn compounds, including some organics and residual medications.
   • Especially useful in tanks that experience chemical buildup or after dosing antibiotics or treatments.
3. Enhanced Detoxification
   • Better at neutralizing hydrogen sulfide, ammonia, and certain toxins that may build up in low-oxygen or high-bioload systems.
4. Longer-Lasting (in Some Cases)
   • Because of its enhanced reactivity, you may be able to use smaller amounts or change it slightly less frequently—though this depends on your system’s demand.

 

[Christoph]

Does that sound plausible to you, Christoph (an expert chemist who has actually measured trace binding to GAC)?

@Christoph

We have not directly compared differnet brands/types of carbon - since usually carbon is based on natural products, there will always be some variation regarding elemental content and behaviour. For example most carbons leach significant silicon, we have also seen carbon as a source of manganese for example.

BR, Christoph

 

[ShawnSaucier]

In my past systems, I do my water changes with the system running.
For the first water change I will turn off the power and add fresh saltwater to my sump. This would determine how much I can safely add without a disaster happening if there is a random power outage ( muphy’s law) during future water changes. Once I have that measurement, I will mark the inside of my brute on wheels. This is usually 15-20g-ish.
Once I have these measurements I’ll pump the fresh S. water into the display, kill power to the brute pump and pinch the hose with a clamp. Let the fresh SW mix in the tank while I empty and clean my skimmer cup and top off or maintain anything else. Unclamp the hose, and back flow water back in the brute to the measured line. Takes about 20 minutes at the most every two weeks. This is all done with return and power heads running. My Apex’s programmed “ water change” mode only turns off certain things like ATO, skimmer , ReefMat and a few other elements that are dependent on water level during this time.
I have a new system that should be up by the end of August, beginning of September. Finally…
Not sure what the total volume will be yet, tank is 48”x30”x30” and the sump is 36”x27”x16”.
Would love to do auto changes, but tank is on opposite side of the house from the mixing station. Would be a nightmare running lines…..

 

[Reef'in Rob]

Water change? Whats that?

 

[bluecheese]

As we all know, one of the requirements for owning a reef aquarium is the need for maintenance including water changes, at least for most of us.
Some of us simply siphon the water while many also utilize automatic water change units and some simply replenish lost water from Evaporation.

How often do you perform water changes and by what means?
What is your frequency of water changes?

I do a 2-3 gallon water change every other day and my reasoning is to keep phos and nitrate in check while maintaining traces and elements. It was a method used by a few aquarist friends in the industry and I've seen a huge difference with both fish and coral health

10-15% water change a week.

I keep water pre-mixed in a Brute can, which holds 35 gallons. So I'll change 10 gallons for two weeks while the 3rd week gets the remaining 15 gallons.

 

[Sushinko]

As we all know, one of the requirements for owning a reef aquarium is the need for maintenance including water changes, at least for most of us.
Some of us simply siphon the water while many also utilize automatic water change units and some simply replenish lost water from Evaporation.

How often do you perform water changes and by what means?
What is your frequency of water changes?

I do a 2-3 gallon water change every other day and my reasoning is to keep phos and nitrate in check while maintaining traces and elements. It was a method used by a few aquarist friends in the industry and I've seen a huge difference with both fish and coral health

2 tanks, a 40 AIO and a 20AIO. I siphon 2.5 out of 20 weekly and replace with new. I change out 7.5 on the 40. Can't lift the 5 gal buckets so I use a milwaukee battery operated transfer pump and a couple of hoses. I have a mark on the side of the 40 and stick the short hose in and siphon it out with the other longer hose end going out a window. I reverse the hoses and process to top it up. I use quick connects on the hoses to make it easy to switch.

 

[cobraz]

50 Gallon tank with 45 Gallons of water.
Change 10 Gallons out weekly...
Vac half gravel bed every other week.
Under an hour between water change and cleaning.

 

[Michael Adam]

35 gallons every 2 weeks on a 140-gallon system. Put a 40 brute in the room fill and mix. Pump it out the window and pump it back in.

 

[rhitee93]

I've gone from doing 10 gallons (10%) each Saturday to 1 gallon (1%) each day. My system has 108 gallons of water total so I'm cheating a bit on the numbers for convenience. I also tend to miss at least one day a week for one reason or another.

I keep a small pump in my sump, and another pump in my 55gal salt water barrel. Each morning I pump a gallon of new salt water into a jug. Then I pump a gallon out of the sump and pour in the new water. Takes me less than 3 minutes total. Most of that time is because my water mixing setup is pretty far from my tank.

I did the once a week thing for 18 months, and have done the one gal/day thing for about 6 months now. Parameters seem to be more stable now than before, but it is hard to make a direct comparison because of other changes I've made. However, once a day is so simple that there is no "Dread" to doing it. It's actually easier than feeding my fish.

 

[StewL6]

I have a 25 gallon brute for RO/DI and a 55 gallon brute for saltwater mix each brute has a pump. Each pump has a dedicated 35 foot python tube for top off and WC. i take care of four systems 120, 75, 22 and an old 28 JBJ and 40 gallon frag tank tied into the 120.. I change out a whole 55 gallon brute a week. Systems with sumps like the 120 sump, turn off ATO and skimmer fill sump to predetermined level approx 10 gallons remove python tube from 55 brute and run it out to utility sink and Venturi out old water from DT with python hook attachment . Then I reinstall python to 55 brute and move to next system and do the same thing. The hardest tank to do a WC is the old JBJ as it doesn’t have an external sump and WC is done with the Python with marked levels. I can do all the water changes in about 45 minutes. I do have a project on my list to add Hydros Soles to the system for auto WC this winter we will see.

 

[Formulator]

Haven’t changed water since 2023…

 

[Texas_Aquaman]

I have a 100 gallon system. I do a 15 gallon manual water change every 4-6 weeks. This frequency is perfect for my 18-month-old tank. I use the opportunity of siphoning out the water to also vacuum my sand. Also, after taking out the 15 gallons and before adding any new water I take the opportunity to thoroughly (and carefully) clean all the glass using a scraper. I find it is much easier to do a thorough glass cleaning with the lower water level.

 

[Sophie"s mom]

As we all know, one of the requirements for owning a reef aquarium is the need for maintenance including water changes, at least for most of us.
Some of us simply siphon the water while many also utilize automatic water change units and some simply replenish lost water from Evaporation.

How often do you perform water changes and by what means?
What is your frequency of water changes?

I do a 2-3 gallon water change every other day and my reasoning is to keep phos and nitrate in check while maintaining traces and elements. It was a method used by a few aquarist friends in the industry and I've seen a huge difference with both fish and coral health

Hey, just seeing this post from you and I have a question. how many gallons overall is your tank? I am seriously considering switching to a method like this. My actual volume is about 80 gallons. I am thinking about either a gallon a day, or 2 gallons every other day.

 

[vetteguy53081]

Hey, just seeing this post from you and I have a question. how many gallons overall is your tank? I am seriously considering switching to a method like this. My actual volume is about 80 gallons. I am thinking about either a gallon a day, or 2 gallons every other day.

current one is 400 gallons and this little amount makes a huge difference when done daily

 

[Sophie"s mom]

current one is 400 gallons and this little amount makes a huge difference when done daily

WOW! So if you are doing 2 to 3 gallons a day on a tank that size, I could easily do 2 gallons every other day, and that should be fine. I am thinking, that if I go out of town for a vacation or something, I could do a larger change to cover things until I return. I really like this idea. Not only does it seem like a great thing for the tank itself, but seems much , much less daunting on my end.