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

northstarsentinel

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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!
 

anthonymckay

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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!
Your saltwater TDS values are due to elements you want in your water. Tap water has a high likelihood of having lots of elements you don't want in your water that are harmful to fish & corals.
 

ISpeakForTheSeas

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People have done it before with some mixed results - some people have no issues, but others find themselves struggling to keep inverts/corals; the difference is mainly the quality of the tap water from one place to another - some places have nice, clean water while others have terrible water.
I've also heard that there could be heavy metals / ammonia / other harmful chemicals, but don't water conditioners detoxify them?
This part seems to be the key here - no, water conditioners (like Prime) don't detoxify them. You can use things like carbon and cuprisorb to remove some, but there's always a chance that it won't catch everything that's harmful, or that there'll simply be too much of it for those to remove. Other harmful substances may not be remove at all.
So, simply put, while you might be able to use tap water safely, you also might not. It's much safer to just use RO/DI water to ensure the water you're using is top quality.
 

rtparty

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“Tap water” is far too vague and there would be nothing to learn from it as a whole.

Some places have unbelievably clean tap water that is very likely safe to use. Others are Flint, Michigan and tap water kills everything.

Knowing what is in YOUR tap water goes a long way to knowing if you can or can’t safely use tap in your reef.
 

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As others stated, your location is the biggest variable. There is also the issue of your water changing over time. The tds of my tap water can be as low as the high 200s and get up to over 450, just depends, mainly on the level of the water in the lake it comes from. It seems to be the highest in the summer when the lake is normally at its lowest. Not sure if this is done in many places, but our water provider sends out a notice in the March/April time frame that they are going to hit the water supply with a high chlorine concentration instead of the normal chloramine for a couple of weeks to "flush out the pipes".
 

VintageReefer

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I have a whole house water filtration system and while it is not as good as an rodi unit I use filtered tap water for all my tanks fw and sw for over a year and have noticed no issues

It does filter out lead chlorine iron and a bunch of other stuff and is nsf certified
 
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northstarsentinel

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Thanks for the feedback / info everyone! Seems the consensus is that it depends on the tap water and even in the same place water conditions can change over time. I've heard that before but just wanted to know why that was detrimental to corals. @ISpeakForTheSeas It's crazy that products can say on them that they detoxify heavy metals but don't actually do that, thanks for the article.

@Opus I didn't consider tap water changing over time either, and a whole house filtration system like @VintageReefer has could be interesting. I'll probably just stick to my small RODI system, it's not that expensive, it's just a hassle how I have mine setup.

@Andrey Grodno Thanks for that example, it's cool to see it working for someone who has high TDS in their tap water. It would be cool to see how the parameters / salt / metals / TDS in his water changed over the years.
 

yanetterer

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Lbrdsoxfan

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Admittedly I used tap on my own tanks from 1998 until 2010 or so for FW and salt. Just old fashioned conditioner added. Nothing croaked, lol. I got into discus and realized if you stare at them funny they croak and at 20-40$ a fish (back then) that was blasphemy. Went to ro water (since they demand high quality) then when I went back to salt in 2015, I added mixed bed DI.

My pops uses the Paul B method and just collects from the ocean and strains it out. Maybe a slight addition of IORC salt periodically and that's it.
 

mfinn

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I'm another one who started with tap water.
But in my defence no one even mentioned a rodi back in the 80's when I started.
I used my Olympia WA. water for 20+ years and had zero issues.
I never even tested the tds of my tap water until the middle 90's and found that it hung out around 20-25 tds.
No chlorine either.
Then in the late 90's they started using chlorine and I just simply used a dechlorinator.
It wasn't until about 15 years ago I noticed the tds creeping up to 50-60 that I considered going rodi.
There was a lot of debate going on at the time ( and I paid attention to brands, sizes, etc) so I was armed enough info to jump in.
So even today my tap waters tds is only 60-70, but I used my rodi and am happy with it.
 

Uncle99

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My city water posts the use of chloramine, some nitrate and phosphate in waters delivered in order to make it safe to drink.

I’d certainly like to remove at least, those three from my RODI.

Used tap water in the 80’s. For about a year things looked good, then, over the next year just dwindled down but very slowly.

It’s a piece of mind thing, a leap of faith to some degree.
 

KrisReef

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our water provider sends out a notice in the March/April time frame that they are going ... to "flush out the pipes".
Our water provider just sent out a notice that instead of injecting the recycled toilet water into underground wells they are just going to pump in directly back into the tap water system.

Every flush in the City goes back to the tap, and I can taste the difference between Saint Patrick's and Thanksgiving seasons.
 

cilyjr

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Our water provider just sent out a notice that instead of injecting the recycled toilet water into underground wells they are just going to pump in directly back into the tap water system.

Every flush in the City goes back to the tap, and I can taste the difference between Saint Patrick's and Thanksgiving seasons.
You're probably going to get RO water out of the treatment plant then.
Likely all that will be in it is what is leached back in from the pipes getting from there to your house but that could be quite a lot considering most water systems are hundreds of years old.
 

Randy Holmes-Farley

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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.

 

Jdooley

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I always had freshwater tanks growing up and when I switched to saltwater I continued to just use my well water that went through a house filtration system for about two years before I decided to buy a Rodi unit and it’s one of the best decisions I’ve made.
 

ISpeakForTheSeas

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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
It depends on the rainwater, but - given how sensitive inverts are to copper - I wouldn't assume so. To quote the top link below, "copper was above the ADWG (2.0 ppm) in eight samples out of 365 samples," (ADWG meaning Australian Drinking Water Guidelines) - 2.0 ppm may not seem like much, but it is substantially higher than the ~0.002 to 0.2 ppm LC50 of Copper.
 

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