9.2 PH Tap Justify RO?

[RomCOM]

I'm beginning to put together my first aquarium. Among the many variables I'm trying to make the most informed decision on (EG: substrate, filter, light volume/spectrum, etc), my tap water has stumped me the most. The API test kit for "high PH" caps out on my tap water. Looking at my location's water reports, that reading is accurate as it averages around 9 PH with regular spikes into 9.3 PH. Letting the water sit for 2 days to equalize CO2/O2 did not budge the API PH test. Granted it could have dropped it to 8.8, since that's the max reading for the test. From my reading I know that PH normally isn't too important barring specific plants/fish. I feel like those sources though are normally expecting PH more in the 6-8.5 ranges. Unrelated but my water is also relatively hard (9.95dGH) and alkaline (6.4dKH).

My concern is high PH will make any mistake on my first tank much more deadly due to Ammonia and Nitrate toxicity at that level. I'd also like lower PH as I've heard it make nutrient absorption from plants more efficient and I intended to have a heavily planted tank. Finally, a lot of active substrates buffer PH and become depleted much quicker in high PH water.

Does the above justify a move to RO/RODI water, or is there a method for handling these type of parameters that I'm just not aware of? Or, more typically of me, am I overthinking the entire thing?

Water report attached if anyone is interested or wants to confirm I have accurate numbers:

 

[hypnogogia]

If you look at the journals section you’ll see some amazing aquaria in hard water areas using tap, so your water parameters are by no means limiting. Are you planning on using CO2? That will lower ph as well.

 

[RomCOM]

My general intent is to be a no CO2 tank. Current plan is Tropica Substrate with a gravel cap and sponge filter + air stone combo for aeration/water movement. It's a 20 gallon/75 liter tank and I intend to have submerged, floating, and emersed plants at tank startup. I was considering a heater as well, a cup of water in the tanks future position read about 67f/17c which is on the low side.

On the fish side, I am planning on waiting a few months to see what the tank looked like at stable parameters then selecting a light stocking of whatever fit said parameters best. I might add some snails/shrimp earlier than that to help keep the tank under control as well.

 

[Andy Pierce]

The alkalinity listed in the report is not high enough to drive the pH over 9. I suspect they have added NaOH to deliberately raise the pH of the water. @dw1305 I believe mentioned this is sometimes done to prevent pipe corrosion? If you're comfortable measuring alkalinity it is pretty straightforward to reverse the elevated pH by adding a moderately concentrated (1M) solution of HCl. I do this with my tap water and in my case it works out to a little over 50 mL of 1M HCl to neutralise 12L of tap water. Using remineralised RODI water is a very well understood method for getting your water as you would like it for aquascaping and livestock that has a dependence on specific water parameters - that's probably your best approach other than just seeing what does well in your tap water as it comes and going with that. You would have more flexibility if you injected CO2 which will not only make your plants a lot happier but which will also decrease the pH to around (in your case) somewhere like 7.8+ as most people aim for injected CO2 to decrease pH by 1 pH unit.

 

[RomCOM]

My thoughts are similar. If I'm going to have to start making chemical adjustments to make my tap water into a workable state, I might as well make chemical adjustments to RODI water. That way I'm at least getting complete control of my water for the effort I'm spending. My local fish shop did recommend just cutting the tap with 50% RODI, but I feel then you're in a similar boat where you've got to account for the fact I'm not just diluting the PH, but every other mineral content in the water.

 

[dw1305]

Hi all,

The alkalinity listed in the report is not high enough to drive the pH over 9.

It is very different as tap water from what we get in the UK. I wonder if the pH reflects the <"evaporite minerals"> in the aquifer? There is a <"huge amount of sulphate (SO4--)"> at 240 mg / l, quite a lot of sodium (Na+) - 76 mg / l etc.

This is the <"Cretaceous age sea covering the mid-west of the USA">. It flooded, evaporated and re-flooded the mid-west over an extended time period.

I suspect they have added NaOH to deliberately raise the pH of the water. @dw1305 I believe mentioned this is sometimes done to prevent pipe corrosion?

It is in Europe, I'm <"not sure about in the USA">.

If I'm going to have to start making chemical adjustments to make my tap water into a workable state, I might as well make chemical adjustments to RODI water.

The water report for Omaha <"doesn't sound great">. You don't need the DI polishing resin, RO is fine to use.

Omaha (Metropolitan Utilities District)
The land-locked city of Omaha gets its water from the Missouri and Platte Rivers, as well as from groundwater. Of the 148 chemicals tested for in Omaha, 42 were detected in some amount, 20 of which were above health guidelines, and four of those were detected in illegal amounts. These were atrazine, trihalomethanes, nitrate and nitrite, and manganese. Atrazine is an herbicide that has been shown to cause birth defects. Nitrate is found in fertilizer, and nitrite is used for curing meat. Manganese was detected at 40 times the legal limit during one month of testing.

cheers Darrel

 

[RomCOM]

It is very different as tap water from what we get in the UK. I wonder if the pH reflects the <"evaporite minerals"> in the aquifer? There is a <"huge amount of sulphate (SO4--)"> at 240 mg / l, quite a lot of sodium (Na+) - 76 mg / l etc.

Welcome to the Bread Basket, where you're never more than 20 minutes from the nearest corn/wheat/soy field or cattle ranch. I'm also in a red zone in regards to areas that don't use buffer zones for fertilized fields. The sodium is likely sourcing from the road salts that are put out in the winter to keep ice off concrete. I wish we'd use sand. It's got it's own drawbacks, but it's not nearly as devastating to the local ecology if handled correctly.

The water report for Omaha <"doesn't sound great">. You don't need the DI polishing resin, RO is fine to use.

They've improved since I got here at least! I'm not sure what data that was pulled from, given it sourced from a news org called "24/7 Wall St". Water system violations listed for my district just list <"only 5 total recorded violations"> sourcing from the EPA, but there might be a data set I'm not seeing that's more damning. My primary concern is some pretty large spikes in Chloramine treatments. From my understanding I thought deionization (EG: RODI systems) handled that better but now after checking it appears I'll need a specialized carbon filter to put in front of the RO filter.

 

[dw1305]

Hi all,

My primary concern is some pretty large spikes in Chloramine treatments. From my understanding I thought deionization (EG: RODI systems) handled that better but now after checking it appears I'll need a specialized carbon filter to put in front of the RO filter.

Chloramine is a potential issue. You need @ian_m to comment on RO and carbon filters.

Welcome to the Bread Basket, where you're never more than 20 minutes from the nearest corn/wheat/soy field or cattle ranch. I'm also in a red zone in regards to areas that don't use buffer zones for fertilized fields.

Yes, we have similar problems in the <"S. and E. of the UK">, not as bad as yours, but as the <"Brexit bonus"> kicks in it <"will only get worse">.

The sodium is likely sourcing from the road salts that are put out in the winter to keep ice off concrete.

It maybe, I think it could also come from the Platte river? I know that there are trona deposits in Wyoming and also the effects of abstraction would reduce water volume.

They've improved since I got here at least! I'm not sure what data that was pulled from, given it sourced from a news org called "24/7 Wall St". Water system violations listed for my district just list <"only 5 total recorded violations"> sourcing from the EPA, but there might be a data set I'm not seeing that's more damning.

That is good news.

cheers Darrel

 

[Maf 2500]

Your nitrate levels are very low so one positive is that it does not look like much farm runoff is making its way into the Omaha water supply. By contrast I get 20ppm nitrates gifted to me by the water company, and much of lowland England is similar.

Another option to consider, maybe in conjunction with RO, is if you have the ability to collect and store rainwater? - that would be a "clean enough" source for aquarium use.

 

[RomCOM]

Your nitrate levels are very low so one positive is that it does not look like much farm runoff is making its way into the Omaha water supply. By contrast I get 20ppm nitrates gifted to me by the water company, and much of lowland England is similar.

Another option to consider, maybe in conjunction with RO, is if you have the ability to collect and store rainwater? - that would be a "clean enough" source for aquarium use.

The nitrate levels did stump me. If I go back to June they're reaching 17mg/L like I expect, but the yearly recap for 2023 indicates that peak for both nitrite & nitrate was 2.78ppm. I thought mg/L to ppm was 1:1 but maybe I'm mistaken. Could be that 2023 was just a good year for nitrates. If I had to guess it'll spike around spring since the largest application of fertilizers happens around then.

Either way I think my plan is just going full 100% RO water and find a remineralization regime that works for me. Rain water sounds tempting but I'd rather just store a RO system in my utility room sink as opposed to finding a place for a rain barrel.

 

[MichaelJ]

The water report for Omaha <"doesn't sound great">. You don't need the DI polishing resin, RO is fine to use.

A pH of 9.25 out of the tap is quite unusual and pretty far off from the EPA's NSDWR recommended range of 6.5 to 8.5. I wonder what the reason is for this - likely the addition of NaOH (which is bad) as @Andy Pierce suggest (Na / Sodium at 76 ppm supports this theory). I any event, @RomCOM, if it's practical for you, you should use RO water - it will give you a predictable starting point.

Cheers,
Michael

 

[Maf 2500]

The nitrate levels did stump me. If I go back to June they're reaching 17mg/L

If I had to guess it'll spike around spring since the largest application of fertilizers happens around then.

Seasonal variation makes sense. Yet another reason to go RO if water composition and quality varies greatly during the year.

 

[Maf 2500]

OK I have a question that is slightly off topic, so apologies to OP. Maybe @dw1305 or @MichaelJ or @Andy Pierce will know the answer....

The OP's water report indicates a very low level (0.1 mg/l) of OH. Does this indicate that NaOH has not been injected? Or alternatively could it have been introduced but the OH reacted with other contaminants to form new compounds leaving behind the Na? Or do we not have enough information to know either way?

 

[MichaelJ]

leaving behind the Na?

Yes, NaOH also known as Caustic Soda is highly reactive. I am not a chemist, but I suppose it would react quickly with other compounds and leave the Na behind. @Andy Pierce et al can provide more and better insights.

Cheers,
Michael

 

[RomCOM]

OK I have a question that is slightly off topic, so apologies to OP.

No sweat, I got my answer already so a minor topic changes are welcome. For example, and completely unrelated, if people wanted to start listing of their favorite RO filters or remineralization strategies I wouldn't mind. No reason obviously.

 

[Aqua sobriquet]

RomCOM, looking online you get just over 30 inches of rain a year in Omaha, any way you could collect some of that?

 

[Andy Pierce]

OK I have a question that is slightly off topic, so apologies to OP. Maybe @dw1305 or @MichaelJ or @Andy Pierce will know the answer....

The OP's water report indicates a very low level (0.1 mg/l) of OH. Does this indicate that NaOH has not been injected? Or alternatively could it have been introduced but the OH reacted with other contaminants to form new compounds leaving behind the Na? Or do we not have enough information to know either way?

I don't think this tells us very much.

Listing the hydroxide concentration [OH-] is a backhanded way of reporting the pH so I don't think it's a formal statement that they added hydroxide (even though I suspect they did or that there was a source of hydroxide in the water supply). 0.1 mg/l is not "low"... at 25C this would mean the pH is 8.77.

More details: pH is (by definition) a measure of the H+ concentration and in water there is an equilibrium where [OH-][H+]=1e-14 (at 25C). Their listing of [OH-] = 0.1 mg/L is vaguely consistent with their reported pH of 9.26. The inconsistencies may be explainable because pH is temperature dependent and they don't specify the temperature they did the pH measurement at and because they only list the [OH-] concentration to 1 significant digit so it could be as low as 0.5 and and as high as 1.5.