Why is my water turning Alkaline

Maybe try to get your water from another source. Rain water or from a creek or river. Look for other water sources.

I've got to admit it's making me nervous but Byron seems to know what he's talking about

I don't have a practical alternative water source unfortunately (City living). I'd actually got to the point where I was considering an RO setup but I really don't want the extra hassle.

FunkyDexter said:

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?

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FunkyDexter said:

I don't have a practical alternative water source unfortunately (City living). I'd actually got to the point where I was considering an RO setup but I really don't want the extra hassle.

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You seem to have a fear of your pH...believe me, it is OK. I'll answer the CO2 question after I've offered some general comments.

An aquarium with fish present will become biologically stable when it has established, which usually takes a few months. If the fish load is maintained, fish are fed regularly the same, water changes are regular with respect to frequency and volume, plants are growing (or no plants, whichever), and additives other than conditioner and plant fertilizer are avoided, the water chemistry will become stable and remain so. The pH will be relevant to the GH/KH and the afore-mentioned factors. This stability has existed in my tanks for over 12 years. When I test pH, which I rarely do now because reguylar testing for two or three years showed me things were stable, the pH in any given tank never varied by more than a couple of decimal places. Tank 1 had a pH of 6.2 to 6.4 for years, tank 2 was 5.0 for years, tank 3 was below 5, and so forth; each tank established its unique biological system and it remained constant. That is or should be the aim.

The problem is when the aquarist decides to interfere with the science. Adding CO2, adding this or that chemical substance to affect pH or whatever--this is when things begin to fall apart and fish become stressed and weakened. This all boils down to something many in this hobby do not understand. This is a totally scientific hobby, and once you put fish in an an aquarium of water, you are bound by the natural laws of chemistry, biology, botany, and microbiology. These laws are what govern life on this planet, and none of us can change them. As soon as we add some substance to "change" one factor, it has a ripple effect throughout the system because that is how natural laws work. If they did not, life as we know it would never exist. We can easily see this in the world today; global warming has already affected several aspects of the natural world like ocean currents from the south pole up the Atlantic.

When the aquarist adds any substance intended to change the pH, that additive is going to bang straight into the laws of nature, and they are not going to bend but they will exert their force. The resulting up and down will cause severe stress to the fish and indeed the entire system, until something gives and breaks. Usually it is dead fish.

Now, to specifically discuss the effects of CO2.

Adding CO2 is harmful to fish. It is true that the fish do not die immediately (though they will if the CO2 increases to a certain level) but they are being impacted. This is why many with high-tech planted tanks do not have fish in the tanks. It is also why those who do have fish will ensure the CO2 is not run at night but increased surface disturbance during the night is added to drive the CO2 out of the water. [The fish are still being negatively impacted but that is another issue.]

I have fairly well-planted tanks, no CO2 though, relying solely on the natural CO2 produced not only be the normal respiration of fish, plants and some bacteria species (which is 24/7 night and day), but also and primarily by the decomposition of organics by various bacteria in the substrate. During the day the plants use the CO2 [I needn't go into the balance aspect, it is not directly relevant here], and during darkness they do not so it rebuilds. A few years ago I happened to be in my fish room just after the tank lights came on, and I noticed the cories in the 70g tank were sitting on the substrate respirating very rapidly. Obviously there was a problem with the water, but tests came out normal. After a few hours, I noticed the fish were back to normal. Next morning, same thing. Then it struck me that the probable issue was the increase overnight of CO2 so I adjusted the filter return to cause a stronger surface disturbance at that end of the 4-foot tank. Problem solved, and never returned. The buildup of CO2 was enough to affect the fish. It is just not wise or safe to be adding CO2.

As Byron states above you can run tanks at almost any pH you like and the inhabitants will adjust. The problem with this is that when you go to add new fish to your tank it will give you a headache. That is why I say your fish tank should be kept very close to pH 7. This will allow you to add fish with very few problems.

itiwhetu said:

As Byron states above you can run tanks at almost any pH you like and the inhabitants will adjust. The problem with this is that when you go to add new fish to your tank it will give you a headache. That is why I say your fish tank should be kept very close to pH 7. This will allow you to add fish with very few problems.

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If most of us acquire new fish from a local store, chances are they use the same tp water and probably do not do any adjustment re the pH. At least, my local stores do not. And as this pH is what occurs from my tap water, there should be no issues. If one is acquiring fish requiring a different pH, and has a tank prepared with such water, example an African rift lake cichlid tank with very hard and basic pH water, that is another matter. GH and pH buffering/adjustment would be a standard feature of such a tank.

Byron said:

If most of us acquire new fish from a local store, chances are they use the same tp water and probably do not do any adjustment re the pH. At least, my local stores do not. And as this pH is what occurs from my tap water, there should be no issues. If one is acquiring fish requiring a different pH, and has a tank prepared with such water, example an African rift lake cichlid tank with very hard and basic pH water, that is another matter. GH and pH buffering/adjustment would be a standard feature of such a tank.

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You would think that would be the case. But in fact you most probably find that they will do what I did.
I would use natural neutral gravel for my acid loving fish, and a gravel that was Alkaline for my live bearers. We made sure that all the fish would be going into tanks with pH as close to optimum for that fish. Fish are transported across regions and countries, as a LFS this process is only possible if everyone keeps the fish in conditions as near perfect as they can.

In the situation above, this gives the LFS a problem. The person buys a perfectly healthy fish takes it home and it gets sick. Immediately the fish shop is to blame. Not the customer who has their tank set up outside of the range that fish would be expected to live in.

itiwhetu said:

You would think that would be the case. But in fact you most probably find that they will do what I did.
I would use natural neutral gravel for my acid loving fish, and a gravel that was Alkaline for my live bearers. We made sure that all the fish would be going into tanks with pH as close to optimum for that fish. Fish are transported across regions and countries, as a LFS this process is only possible if everyone keeps the fish in conditions as near perfect as they can.

In the situation above, this gives the LFS a problem. The person buys a perfectly healthy fish takes it home and it gets sick. Immediately the fish shop is to blame. Not the customer who has their tank set up outside of the range that fish would be expected to live in.

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If the store did use calcareous substrate for fish needing harder water, and the aquarist does the same, there would be no issue. And if the aquarist does not do this, the fish are going to succumb to soft water regardless.

I am curious with Byron's response to this thread. I am in no position to doubt his wisdom and his description of your setup. What I am surprised at is that Seriously Fish states that these fish should be kept in the pH range 6-7.4. For some reason that does not apply in your case.

Hi Guys and thanks for the further information.

Byron, in particular thanks for post 18 - so no CO2 then. As I said, the plants in there don't seem to need it and I've got no desire to add it if it might make things worse for the fish. I'm learning a lot here

Itiwhetu, I'm concerned about the pH too but I was in the fish shop yesterday and they pretty much confirmed everything Byron is saying. Their response was along the lines of "That pH is really high for that gH but it's the gH that matters and should be fine for Angels".

I really don't like the idea of putting fish in with that pH but all the feedback I'm getting is that it should be fine so I'm going to give it a try with a couple of angels the weekend after next. Neil and Buzz will flap one small fin for a fish and one giant fin for fishkind. I just hope it's Apollo 11 and not 13.

Adding CO2 to control pH is not the way to go. You will need a solenoid and pH controller. this will monitor the pH and add co2 as needed to maintain the pH you choose. I ran co2 for over a decade on a high tech planted tank, So i can warn you about a few things.

When my co2 got low and needed a refill, the bottle was off the tank for a couple of hours. When you get a bottle refilled as opposed to doing an exchange, have gloves, evem in summer. The bottle refilled with be extremely cold, After all cry ice is frozen co2.
Make sure you use teflon tape on all threaded connection. My first 5 lb. bottle ran out in under 2 weeks. Then I taped everything. Then it lasted for months.

When one lowers pH using CO2 it is different than using other methods. If the co2 stops being added the tank will return to normal co2 levels and the pH will move back up to its natural level,

I would urge to read here to get a better understanding of this all https://fins.actwin.com/mirror/begin-chem.html#reference
it is written in plain English and is fairly easy to understand.

p.s. I do one tank with a low pH and TDS. I use RO.DI water and mix it with my tap. RO/DI water is almost pure and it has no KH or GH. It would have a neutral pH except that it will absorb co2 and that will make it acid.

Thanks for that. Following Byron's last response I've already decided I'm not adding CO2. Interesting article.

Enjoy your fish. I hope things work out well for you

Thanks. I'm really looking forward to popping them in.

I'd been meaning to post back on this. Neil and Buzz have been in the tank for fortnight now and are doing great. They hid away at first (I guess they were just being a bit koi) but settled in after a few days and have really started owning their new home. I'm planning on adding a couple more this weekend. Thanks again to everyone for your help.