Seeing benefits from using tap water

[Mebbid]

Disclaimer: I am in no way, shape, or form suggesting that people use tap water. Mine is higher quality than most I've seen and as such shouldn't be viewed as me condoning the practice regarding usage of tap water in reef tanks.

Now, the reason for this post:

My reefing experience is coming up on 2 years now and through that time I am seeing the exact same trend between my 20g that I started with and the 90g that I have now.

In both of these tanks I have been unable to feed my fish enough to impact my water parameters. No matter how much I feed, the readings stay at 0ppm of both nitrate and phosphate. In my 20g I was feeding 1/3 of a cube of frozen mysis daily to 3 fish. I moved that up to half a cube daily in my 90g with the same results. Due to a fish that's highly aggressive if he doesn't get frequently, I have increased my feedings to a large number of pellets twice daily with every other day nori. The parameters stay the same at 0.0ppm of both phosphate and nitrate. In both of these tanks the growth of my macro algae is extreme which is obviously what is consuming my nitrate and phosphate overload.

My point in all this:

Due to my using tap water which has higher levels of nutrients, most notably potassium than the ro/di water that is used in most reef tanks it isn't limiting the growth of my macro algae.

Leibig's Law (Liebig's law of the minimum - Wikipedia, the free encyclopedia)
would point to agree with me where it is summarized as "Only by increasing the amount of the limiting nutrient (the one most scarce in relation to "need") was the growth of a plant or crop improved."


Why does it matter?
A further method of nutrient control in our tanks could be as simple as a small addition of potassium.

 

[Animal-Chin]

I'm missing how potassium is the magic element here? I mean I use RO water in my reef and my macro in the sump grows like crazy, I have to remove handfulls all the time. My macro is growing because of the light over it and I'm guessing the nitrate and phosphate its sucking out of the water. Did you do a test where you had macro algae with in your system with high potasium and then with low potasium and record the difference? I'm missing the control element of your conclusion here.

 

[Sniperhank]

I read an article about potassium in reefs a year ago, but the outcome that they came to is that it can hold some importance, but not enough to dose or even test for.

 

[Gregcoyote]

I have also researched this and even bought a potassium test kit. I found feeding provided more than enough potassium and additional added thru the water source or dosing was anti productive. Same with iodine.

The issue (and you covered it in your disclaimer) is that every city has a different set and acceptable level of pollutants in the water supply. You can test for the obvious ones like iron, lead, copper and organics. But there are even more there that a hobbiest can't test for. And where those may be in acceptable amounts for humans, being concentrated in your fish tank thru distillation (evaporation) can become deadly to corals and fish. Keep it simple and start with pure water. Then you decide what gets added based on chemical tests. JMO

I'm NOT saying that there aren't some communities that have acceptable tap water for reef use, but even in those settings the city can make changes that affect the water quality without your knowledge. I know Mr_X uses tap water where he's at with no issues at all, but for the reasons above I wouldn't choose to use it. My city barely can run traffic lights much less guarantee water quality.


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[Animal-Chin]

To me the only way we can attribute success to potassium is if a controled experiment was done where all elements were measured then only potassium was elevated and we saw results. Not having nitrates and phosphates could be a result of multiple filtering systems working together and regular water changes.

 

[SeanMonster]

I agree with Mebbid in that Great Lakes water is very good. I live in western NY and used to use tap water as my lfs told me that our water quality is awesome. I did switch to RO/DI though because of one thing the owner said. Suppose their is a water main rupture or the water authority does work on the system? You could end up with a "slug of crud" that you add to your tank unknowingly and then your tank is fried. I just figured that, while chances were small, the state and age of the infrastructure around here the RO/DI unit would be a cheaper investment in the long run.


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[mr_X]

Like Greg said, I've been topping off a 200 gallon system with treated tap water for probably 7 years now with no ill effects. That's about 10 gallons a week for 7 years. That said I make the water changes at my house with RODI (and lug 24 gallons of salt water 45 minutes to the tank), and if I had it my way, I'd be topping off with same. I have warned the tank owner and he doesn't seem to care, and will not install a RODI in the building, so I do the best I can with what I am afforded.
Miraculously, the tank is bulletproof. I do not condone the use of tap water for all the reasons mentioned above, and you sure won't see me putting MY municipalities water in my tank.

 

[Gregcoyote]

If it works long term, don't mess with it. I wouldn't carry that much water either.


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