Why is my water turning Alkaline

[FunkyDexter]

Apologies if this isn't exactly the right forum, it seemed like the best fit. I'm also not really looking for a definitive answer here - just some ideas I can investigate.

I'm currently cycling up a new aquarium, intended for angels so I'm looking for a PH of, ideally 6.5. The thing is, I can't get the ph down to anything like that level. I've tried a few things, some planting, some catapa bark but it's still riding high at about 8.5.

The thing is, my tap water is somewhere between 7 and 7.5, meaning the water is gaining ph after it comes out of the tap.

My first thought was that perhaps something in the tank was leeching into it, I've got a lot of rocks in there and a sand base. So I took 3 bowls of tap water, added sand to one, a rock to another and nothing to the third. The next morning all three had increased to a PH of 8, implying that it's nothing to do with the rocks or sand (or at least some other factor was still at play).

My second thought was that perhaps the bowls I used had somehow leeched in so I repeated the experiment using glasses. I couldn't actually fit a rock into any of my glasses so I just tried the sand and an empty control. Same result, the next day the alkalinity increased to about 8 in both cases.

My third thought was that perhaps the water filter I have on my kitchen tap (which is where I've been drawing the water from and has an ordinary domestic tap water filter) might be leaving some chemical in the water that has a delayed reaction. So I tried taking some water from my outside tap as well as a second sample from the kitchen tap. Next day both are up to ph 8.

In all of the above cases I tested a sample of tap water immediately after it was drawn and confirmed that it was 7.5 in each case

That's as far as I've got at the moment but I'm completely mystified as to what I can try next. It seems like something about my water supply causes it to gain in alkalinity after it's drawn - which is weird, frankly. Although it's only rising to 8 over night it seems to continue rising thereafter, hence the 8.5 I'm seeing in my aquarium (which has had longer to sit). This is looking like a total show stopper at the moment as it'll be harmful to anything I put in there.

So I'm really just throwing this out there to see if anyone can think of anything else I can investigate. Or whether anyone has ever seen anything like this before. Any help would be welcome and all straws will be clutched at.

Thanks in advance.

 

[Myraan]

The raising in the bowls you see is the de-gassing of the CO2. A portion of the CO2 dissolved in the water will ionise into carbonic acid, depending on how much kH you have. Damage to coral from ocean acidification is an actual positive feedback worry due to increased CO2 in atmosphere.

If you are cycling, I assume you adding ammonia or similar? I found the ammonia itself would cause an increase in pH. As more nitrite was produced I had a pH crash; I assumed at the time the nitrogen salts themselves were acidic (nitric acid); but it might have been a combination of the loss of the ammonia and the added biological activity producing CO2 through respiration. Tank was full of copepods and planaria at this point also (I assume these are also normal but fish usually eat them as fast as they appear)

 

[Byron]

@Myraan is correct on the CO2 issue. The pH of your water is in fact 8.0 not something lower.

The pH is closely connected to the GH and KH, and the three parameters must be considered together. GH is the level of dissolved calcium and magnesium (primarily) in water, and KH is the carbonate hardness or Alkalinity. Both of these directly impact pH, and the higher the GH and KH are, the more buffering of the pH will occur. Not that I suggest you do or need to do this, but changing pH as by lowering it must take into account the GH and KH and they too must be reduced. CO2 is also a factor, as the tap water out-gassing shows; the more CO2 in the aquarium water, the lower the pH because CO2 produces carbonic acid. The GH and KH factor in as I've said.

What is the GH and KH of your tap water? These numbers will tell you/us what to expect with respect to the pH. If the GH and KH are fairly low, the water is soft and buffering capacity is minimal so the pH will naturally over time lower due to the increase in decomposition which produces CO2. Plants enter the equation too. There is a natural diurnal fluctuation in pH in nature and in aquaria. This is why it is important when testing pH of aquarium water to always test at the same time of day so you get a more reliable idea of the long-term pH. It will be lowest in the early morning after the night, and highest in the late afternoon.

 

[FunkyDexter]

The raising in the bowls you see is the de-gassing of the CO2. A portion of the CO2 dissolved in the water will ionise into carbonic acid

That makes sense and a CO2 kit was already next of my list of possible solutions to try.

If you are cycling, I assume you adding ammonia or similar?

Just adding a bit of food to decompose at the moment. It'd probably be easier with ammonia as the food has a delay but I've seen it produce and deal with ammonia and nitrites, though not in very significant quantities yet.

I'll test the Gh and Kh tonight. I did test it when I set the thing up and made sure they were in acceptable limits for the fish I wanted (they were) but I didn't make a note of the actual numbers.



Edit>Kh and Gh are 9dKh and 10 dGH respectively

 

[Myraan]

Have you been testing for ammonia, nitrite and nitrate?

 

[Byron]

Kh and Gh are 9dKh and 10 dGH respectively

This is moderately hard water, to use a subjective term. No problem for angelfish that are tank raised (not wild caught).

As for the pH, there is sufficient buffering here that it is not likely to lower much. I would leave things as is.

 

[FunkyDexter]

Have you been testing for ammonia, nitrite and nitrate?

Yes, currently showing zero except for some very low levels of nitrate. I previously got the ammonia to roughly 5 ppm which then cycled through. Nitrates went to about 2 and has since declined to zero. I'm pretty confident I've got the bacteria I need now so I'm really just concerned with the PH issue.

Also, correction to above: you told me to test my tap water but I tested the aquarium water in error. The tap water levels are 9dKh and 12 gKh (although that started changing colour on the 11th drop so you could call it 11.5)

As for the pH, there is sufficient buffering here that it is not likely to lower much. I would leave things as is.

OK. Just to be clear, are you saying just give it more time and the Ph should start to drop? You're not saying I can start introducing fish yet are you?

 

[Myraan]

I suppose algae and/or plants could be using up all of the available CO2, so that there is now even less than degassed tap water.

pH greater than 8 seems high for 9gH water, but I'm no expert.

Maybe you are overthinking things and the presence of of fish respiring will make things more normal.

 

[Byron]

On the GH and KH, no issues. The plants are likely using some of the calcium/magnesium. As for pH, it may or may not lower. A KH of 9 dKH is probably going to do some buffering of the pH to prevent fluctuations (changes, which is why your attempts to lower it will not work, the buffering will bring it back up and that is far worse on fish). Leave it alone. Over time (a few months) as the aquarium establishes--this is different from just cycling--the chemistry will stabilize and you will know what to expect.

Other things also affect pH, and I am no chemist, but the bottom line is, leave it alone and see what stabilizes. The water authority may be adding something to increase pH [I have this here], or some other factor.

 

[FunkyDexter]

Thanks for all the info so far, guys, but I don't think I understand what's being suggested (sorry if I'm being a bit thick).

I guess what I'm asking is, what's my course of action if I want to go from where I am now to a point where I can put a couple of angels in?

If I'm reading your last post right I think you're saying that the kH buffering (normally a good thing as it prevents rapid fluctuations) will prevent the pH dropping (so not such a good thing in my case). Have I understood that correctly? Or are you saying that the buffering will slow down the pH drop so I just need to be patient?

 

[Byron]

Thanks for all the info so far, guys, but I don't think I understand what's being suggested (sorry if I'm being a bit thick).

I guess what I'm asking is, what's my course of action if I want to go from where I am now to a point where I can put a couple of angels in?

If I'm reading your last post right I think you're saying that the kH buffering (normally a good thing as it prevents rapid fluctuations) will prevent the pH dropping (so not such a good thing in my case). Have I understood that correctly? Or are you saying that the buffering will slow down the pH drop so I just need to be patient?

I cannot predict exactly, but let's consider the two likely options. First, let's assume the pH is not going to change because of the GH, KH, etc. I said initially this was not a problem for angelfish. The GH is the more crucial parameter (aside from temperature), and the GH here is fine for tank-raised angelfish. So from the perspective of the parameters, you are OK.

Second, the pH may lower as the tank becomes established. Every tank is a unique biological system. When I had eight tanks in my fishroom, the water in all was the tap water with zero GH/KH. The pH stabilized in each tank at some level, of its own. One tank was in the low 6's, another was well below 5, etc. Yet the water changes with identical water were the same, fish load much the same, live plants, feeding was similar amounts. As your tank settles, with fish (and plants?) it will do what it will in terms of the pH.

Moving forward--another issue has now arisen, when you say "a couple of angels." I might as well warn you of what might well occur. The tank size is not given, so I will simply deal with numbers of angelfish for the present, but realize that if the tank is not large enough this will simply not work at all.

Angelfish are a shoaling species. They live in groups, smaller groups than fish like the characins, but still groups. They develop an hierarchy. Males are territorial, to varying degrees. In too small a tank space, or with too few angelfish, this is not going to end well. A dominant male will decide he owns the tank space. In their habitat, this is no problem because the other males can just move off, still remaining within the collective group but easily get out of harm's way. In all but a very large aquarium, this does not work. A group of five or six is absolute minimum for this species, and this requires at minimum a 4-foot long tank. But that is only the first stage.

If a male decides to pair up with a female and bond, the other angelfish are going to feel the wrath of the bonded pair. If the other angelfish include males, they will likely be hounded to death in a small tank (4-feet), and if females, maybe or maybe not. Individual fish can exercise their natural behaviours to varying degrees. Two or three or four angelfish in any tank will not work, unless they are all females (maybe then), or there is no over-dominant male. A "pair" requires the two fish to select one another and bond; any male and any female placed in a tank may or may not work out. If the pair select each other from a tank of several angels, they may do well together, but there is no guarantee.

 

[FunkyDexter]

Thanks for the information. That's really useful. So I think I'm going to install a CO2 system, give it a couple of weeks and then, as long as the Gh isn't moving, I'll start introducing fish. I can't thank you guys enough for your input.

Re. the number of angels, I wasn't clear on that so sorry for the confusion. I'd already done my research on that and the ultimate plan is 8. (I said I'd be introducing 2 but that's just because I want to introduce them gradually and not overload the tank straight from the off.) It'll be exclusively juveniles so I'll have plenty of time to settle a decent sized shoal in before they start getting frisky.

I'm also intending it to be an exclusively angel tank with the exception of clean up crew (haven't quite settled on that yet but probably a bristlenose, snowball or zebra plec - I really like the zebra and consensus on the net seems to be that it'd get along fine but I'm a little nervous that it's shyness might get it bullied a bit) so there shouldn't be any issue with inter-species rivalry.

edit> I should add for context, it's a 300l tank.

 

[Byron]

OK. That tank will be OK initially, but not if a pair forms. This requires an 8-foot/240 cm length tank or larger.

I am confused about adding CO2...why? Is this to be a high-tech planted tank? You should never add CO2 to a tank with fish.

 

[FunkyDexter]

It's planted but not particularly: heavily 3 swords and 4 mid sized plants. The plants seem to be thriving so far so I don't feel the need to add CO2 on their behalf.

My thinking with the CO2 was that I've heard lots of suggestions that this brings the Ph down so it seemed like a beneficial measure. Are you saying that the side effects (lower oxygen, I imagine) would outweigh the benefits?

 

[itiwhetu]

Personally I would never add Angels into a tank with a pH of 8. But lets see how they get on. The experts in this field have said they will be fine. I'm going to be interested in seeing what happens.