Has anyone tried a long term experiment using tap water vs RODI water for a reef tank?

crazyfishmom

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One of the first things you hear when you get into saltwater is that you should ONLY use RODI water. It's so pervasive that I don't know anyone that doesn't use RODI water (granted I don't know a lot of reefers). On the other hand, virtually no one uses RODI water in freshwater tanks.

Forgive the basic question but, is there a reason why treated tap water would not work in the long term? Has anyone tried a long term experiment to see how reefs do with tap water?

- I've heard that the base TDS could rise overtime as tap water has high TDS compared to RODI. Salt water has a very high TDS though, wouldn't the amount in tap water vs RODI be negligible once you add in your salt? Plus wouldn't regular water changes prevent a buildup?
- I've also heard that there could be heavy metals / ammonia / other harmful chemicals, but don't water conditioners detoxify them?
- I've also heard that it can cause an algae bloom if you use tap water suddenly insted of RODI. But this is just a chemical imbalance that would level out as the beneficial bacteria / clean up crew adjusted to the new nutrient levels right?

So I'm curious if anyones tried just flat treated tap water before for extended periods. Appreciate anyone's thoughts / experiences using either RODI or tap water. Thanks!
The TDS for the tap water in my town is ~60 which is great for tap water so I thought “why not” and that’s how I filled my first reef tank. I’ve been using treated tap for a long time with fresh water tanks and I have ultra clear water and an almost self maintaining tank.

Enter the reef tank and ugh… lesson in humility. The amount of hair algae was just insane. While some LPS did really well, gonis for some odd reason did awesome in that tank, others did not… torches would wither away. Duncans loved it. Acans did well. My red fire Digi did okay. The rest of anything SPS that I tested would usually be okay for a day or two and then STN would kick in. The phosphates were always at 5 (yes 5, not 0.5) or above and the nitrates were 20-60. Stability was nonexistent.

The only difference between how I run my current system versus how I ran my previous system: you guessed it RODI instead of tap. I guess I also carbon dose now which I did not do from the beginning with my previous tank.

Just my experience. I am sure some tap water out there can support a reef tank without causing issues, but I also know that few sources are likely to.
 

Gregg @ ADP

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It really just depends on where you are and the quality of the municipal water supply.

People talk about TDS in tap water, but often don’t know exactly what those solids are. I run water through RO/DI for clients, but that’s mainly because those are part of a standard reef system. There have been times when that hasn’t been an option, so I would then just take a quick look at the local muni water quality report to see what is in there and how much.

Here in the Chicago area, we have very high quality source water (primarily Lake Michigan). So we start off well, and mostly end well depending on individual municipal water infrastructures and home/building plumbing. In the city of Chicago, the primary issue is lead, which is largely due to aging water lines. The city has made replacing those lines a priority and streets have been ripped up all over the place for the last 4 years or so as they are replaced.

If there is lead present but at a level deemed safe for drinking, I can’t imagine it would have a detrimental impact on your aquarium unless you have the system for decades and decades and could achieve some actual bioaccumulation. There is some copper present, but the highest recorded value was 0.065mg/L…meaning all other tests were below that. That is not a particularly alarming number.

Beyond that, a lot of dissolved solids in tap are various salts, most of which we end up with in our salt mixes anyway or add as supplements.

I have a reef tank in my classroom that I run straight Chicago tap for. No issues.
 
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IntrinsicReef

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It really just depends on where you are and the quality of the municipal water supply.

People talk about TDS in tap water, but often don’t know exactly what those solids are. I run water through RO/DI for clients, but that’s mainly because those are part of a standard reef system. There have been times when that hasn’t been an option, so I would then just take a quick look at the local muni water quality report to see what is in there and how much.

Here in the Chicago area, we have very high quality source water (primarily Lake Michigan). So we start off well, and mostly end well depending on individual municipal water infrastructures and home/building plumbing. In the city of Chicago, the primary issue is lead, which is largely due to aging water lines. The city has made replacing those lines a priority and streets have been ripped up all over the place for the last 4 years or so as they are replaced.

If there is lead present but at a level deemed safe for drinking, I can’t imagine it would have a detrimental impact on your aquarium unless you have the system for decades and decades and could achieve some actual bioaccumulation. There is some copper present, but the highest recorded value was 0.065mg/L…meaning all other tests were below that. That is not a particularly alarming number.

Beyond that, a lot of dissolved solids in tap are various salts, most of which we end up with in our salt mixes anyway or add as supplements.

I have a reef tank in my classroom that I run straight Chicago tap for. No issues.
I also use tap water all over Austin for client's freshwater tanks and the water varies greatly between the different water districts. I see pH out of the tap at 7 all the way to almost 10. Our city has split geography that seems to affect the source water. Out west we are on Cretaceous marine deposits ( limestone) and we have very hard water. East is clay and loam farmland and the water tends to be a bit softer. The water quality also changes with lake levels and drought. I have seen negative reactions of fish when lake levels get low. I don't know if the water treatment plants add extra chemicals to fight higher levels of pathogens? I have found water quality to be very localized and can change over time.
 

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I'm in the Tampa Bay area. In the last few years I've topped off with tap water for a couple of months at a time 3-4 times, and each time resulted in major algae infestations that took months of weekly water changes with good water to get under control.
 

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I forgot to mention, that "good water" meant getting 5 gallon jugs of rodi for top off and premixed salt water from my lfs. Upon recovery I've stopped doing water changes and kept using the lfs rodi for top off. The tank stays stable until I go back to topping off with tap water for awhile.

The tank is currently in recovery, this time using rodi from my own equipment at home, and saltwater mixed using this rodi. Rodi made from the same tap water that has spurred algae issues.

Recovery is going as usual, so I'm convinced that my tap water left untreated is an issue.
 

MarineandReef Jaron

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To answer the OP as someone in the same area. I started my first reef tank close to 15 years ago with tap water like the LFS told me to at the time and nothing died, but I had the worst hair algae I have ever had. It looked like a green forest in the tank. I started doing lots of water changes to lower nutrients but it seemed like each water change just made things worse. I then switched to RO water and suddenly the water changes started making things better. We have really high Silicates in the Phoenix area. Even with RO/DI I still get silica breakthrough showing on my ICP results from my RODI water. I would not recommend using tap water in our area.
 

Roadkillstewie

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Outside Houston, we have a well... '90, hard water... corals seems to love it.

Moved to Arkansas, 40' well... diatom bloom at weeks, added rodi.. DI resin depleted after 60-90gallons. appears a heavy amount of silicates and CO2
 

Paul B

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My pops uses the Paul B method
Your Pops nust be a smart guy. I bet he has an old healthy tank and doesn't have to quarantine or medicate. :beaming-face-with-smiling-eyes:

In 1971 when I started my tank we didn't have RO/DI water. At least I never heard of it. I used New York City Tap water for maybe 15 years with no problems. Then I did a water change and my fish instantly started dying and jumping out. I saved some of them and called the water company

They said it is no problem. They added "Zinc Orthophosphate" to control corrosion in the pipes. I don't know about the pipes but it kills fish instantly. :grimacing-face:
 

GARRIGA

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I'm also of the belief that TDS doesn't tell the entire picture and best know your source and possibly consider other options such Ultrafiltration plus CupriSorb should copper be the one item that Ultrafiltration won't resolve along with now considering Hydrogen Peroxide to eliminate biological(s) that would be of concern. Especially with top off where I'm not at all concerned with ammonia remnants from de-chlorinating chloramines or nitrates or phosphates as my system will resolve those naturally.

When I finally get my main built that won't be filled with RODI as it would take too long and I lack the space to store large volumes of prepared water. Going to be much easier to fill it with tap, recirculate tank water through Ultrafiltration along with a few days of Hydrogen Peroxide then send out ICP and see what remains before adding salt. Fact is I'm going to cycle it with salinity at only 12 ppt as that was successful last build and then adjust as needed by resolving that not wanted and only adding what is. Plus before tank goes up, I'll have already installed a whole home filtration system with a point of use Ultrafiltration for make up water which may or may not go through RODI. My understanding is that our tap of high quality, my house built in 2014 and all plumbing is some form of plastic but not sure of the pipes from the water source although my town is likely less than 40 years old. I know my community was built less than 20 years ago.

Not all tap or well water created equal and best know what you have and how to treat it before assuming RODI is needed. Internet loves to regurgitate without fully understanding. Here's Jake (RIP) talking about his local tap and how he went away from RODI as it didn't impact him.

Not saying all don't need RODI. Saying some don't.

 

Timfish

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Yup. You'll want to look at the water reports from your water utility. (And obviously there still might be trust issues with reports like what happened in Flint MI.) Here's one of my systems that was maintained with tap along with ICP tests.



ICP Tapwater
ATI 90 PBD Tap.jpg

ICP Aquarium
ATI 90 PBD Tank.jpg
 

BeanAnimal

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Oddly you could use L.Erie water w/ o issue more or less sans summer algae blooms…
Same for the Phoenix metro area

Here in Myrtle …. horrible
Better than it used to be... I lived there in the early 90's and it was really bad, it even smelled most of the time. The water in Dasy, Loris, Green Sea, etc. was actually pretty good. Conway was pretty bad. I kept a 55 gallon FO tank in Myrtle Beach for years (21st ave north, then Windy hill and North Myrtle). We didn't have coral back then, but shrimp and inverts lived.
 

BeanAnimal

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Yup. You'll want to look at the water reports from your water utility. (And obviously there still might be trust issues with reports like what happened in Flint MI.)
I think the reports are fudged BS most of the time. They are not random and often not representative of the year round water. American Water has bought up countless municipal water companies all over the country. They are a business for profit and spend the least amount of money possible to stay in compliance and on maintenance, etc. They rotate Chlorine and Chloramine in (as well as other compounds like Paul mentioned) seasonally or every year or two depending on the supply source, age of the pipes in the system, bacterial counts, etc.

We all assume that our tap water is some pristine resource that is filtered and cleaned in a fashion similar to our RO/DO units. Yeah.... no. It is pulled from the aquifer, river, lake or holding pond, run through a rather crude filters (sand filters, or fluidized beds or clarifiers) and has some chlorine or chloramine and phosphate added and down the pipe it goes. In some cases (depending on source, a coagulant and flocculant may be used to grab certain compounds for filtration.

In any case Frogs, beavers, skunks, dead animals, raw sewage, etc all find their way into the holding ponds, reservoirs, etc.

Sleep well... and don't forget that glass of water before bed!
 
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litsoh

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Would anyone be able to take a look at this tap water report that I was able to get from our board of water supply and tell me if it would be safe for me to use in my tank?
Water.jpg
 

BeanAnimal

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Would anyone be able to take a look at this tap water report that I was able to get from our board of water supply and tell me if it would be safe for me to use in my tank?
Water.jpg
As mentioned above, even if the report is "good" that does not mean that the day to day water is the same as the report unless the water source is an aquifer. Most other sources (river, lake, retention pond) are highly variable based on daily and seasonal weather (temperature) and runoff.

That looks like it all comes from wells... so maybe Randy or somebody else can help read the report. Good luck!
 

Nemo&Friends

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I do not have corals, but I have a tank with fish and macro algae and one FOWLR. I have never used TODI water, and just use tap water. First because I did not know any better when I inherited my first aquarium over 13 years ago and then as none of the fish seemed to suffer from it, I just continued to use tap water.
My oldest fish, a damsel inherited along with the tank is still alive, must be about 15 years old.
It is not an experiment as I did not compared with RODI, but my fish are fine. I can't help wandering if it is just another push by the marine fish vendors to just sell more unnecessary equipment.
 

ISpeakForTheSeas

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Would anyone be able to take a look at this tap water report that I was able to get from our board of water supply and tell me if it would be safe for me to use in my tank?
Water.jpg
It could potentially be fine, but based on the copper reading there (90th percentile 0.348 ppm), it could also have enough copper to kill off inverts and corals - personally, I wouldn't take the chance, but some people might.

To say it the way Randy did below - the 90th percentile reading above means that 10% of the water sources tested had copper levels higher than 0.348 ppm.

The report doesn't seem to say the range from all the samples, how many samples were taken or how sensitive the testing process is - it's possible that some sources were low enough to be safe, or that all of them had enough copper in them to be lethal to inverts/corals:
Here's some actual data for what I consider to possibly be the most serious problem with tap water: copper.

New York City Water report for 2022.


Section titled" Lead and Copper Rule Residential Tap Sampling"

356 residential taps were tested.

10% of them had more than 0.194 ppm copper (194 ug/L)
the highest had 3.2 ppm copper

Thus, IMO, for copper alone, the tap water in NYC is unsuitable for at least 10% of the folks living there.

While I do not really have a good understanding of exactly how much copper is OK, Fauna Marin says that ten fold lower values (0.02 mg/L= 20 ug/L) can kill some corals.

Yeah, I haven't looked into corals and copper toxicity much, but I have looked into inverts and copper toxicity a bit and 0.02 mg/L seems about right (for the first quote below, the water quality report was for Oceanside, California, and the numbers used were mg/L):
The "Report of Detected Compounds" at the bottom:
- Looking at the copper specifically, they mention the 90th percentile for 50 homes sampled was 0.245 (this means that 90% of the 50 homes tested had copper levels of 0.245 or lower);
- The testing they use for copper is only sensitive to 0.05.
- LC50 for Copper when tested on different inverts* (a mussel species, an oyster species, a copepod species, and two urchin species - one of the urchins was the sand dollar you have; a different test** used a limpet, a crab, and a mussel) ranged from ~0.002 to 0.2 (LC50 being a toxicology term for the dose needed before half of a given population dies from the toxin); the LC50 varies from one species to the other, and it varies dependent on a number of different factors (such as the bioavailability of the form of copper in the water).

Personally, just looking at the odds of getting a damaging to lethal level of copper in your water, I wouldn't use your water without DI.

*Test Report 1
**Test Report 2
Edit: Also, I don't know if it's a problem for your tank or not, but your water report lists the Vanadium levels as being at or above the "Health Advisory" limit (the limit is 21 ppb, the results ranged from 21-39).
 
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Outlaw Corals

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Ok so i can give you my personal experience on this topic from my 31 years of experience in the hobby, my first ever saltwater tank was a 20 gallon tank and i use tapwater, I remember I just thought at the time that it really didn’t matter what kind of water you used I thought the whole RO water was just a big scam to get you to buy more unnecessary equipment, so for the first decade in the hobby, I used nothing but tapwater, but I always used a conditioner to get the chlorine out and that was it, so at this time I had two tanks running, and I wanted to start experimenting with SPS Corals and for the first 10 years there was a lot of learning involved and I remember thinking that this would probably be a good time to try RO water that it would be much better for the SPS Corals, so I got myself a unit and started making the RO water and immediately I was turned off by it because I saw how much waste water there was. There was more waste water than good water and I didn’t like that at all but I wanted to stick with it for a little while to see if I notice any major improvements with the RO water, so I stuck with it for about 12 to 14 months and didn’t notice any major improvements whatsoever I felt it was more of a waste of water than anything else so I stopped using it and went back to tap water and been using tapwater ever since, I just still use water conditioner and that’s it, my corals are healthy and thriving and that’s all I could ask for, I also stopped doing water changes. I haven’t done a water change in the past 10 months and I can see why it’s better not to do water changes but that’s a whole different topic happy reefing fellas
 

GARRIGA

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To the point of finding copper. If that’s the only item found then one doesn’t need RODI to solve it. Items such as CupriSorb work just fine and this particular item changes color as it gets exhausted. Plus takes out other unknown metals as well.

Again. Not saying to not use RODI but for some their tap might be good enough without it.

If the water analysis provides maximum for contaminants that are tested then one might be able to determine if other means can be used to avoid that as a potential point of concern.

Safest route will always be RODI although not practical for all. Myself won’t have access until whole house filtration installed as I have no place to put it and hooking it up in the spare bathroom will get me divorced. Although there are times that seems pragmatic lol
 

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