pH variation during day and night

[Rafoda]

Hello, everyone!

I have a planted, 38L (not excluding gravel etc.) tank. I've got 3 guppies and 9 white clouds in it. The tap water in my city has a KH of about 1 and is slightly acidic, and I have recently purchased a CO2 cylinder with a solenoid valve.

I am adding sodium bicarbonate to raise both pH and KH. So, here is what is happening: I achieved a pH of about 7.5 and KH of 4. But, when the CO2 turns on, the pH drops to about 6.8 or even less. This would give me a CO2 concentration of about 20 ppm (please, correct me if I am wrong).

Today I read here at the forum that I should have an average of 30 ppm, which would give me a much higher pH day/night variation. And I didn't want to get my pH too low or too high. I would like to mantain a neutral pH, as I read everywhere that guppies need it. I also read here that a one-point pH variation is acceptable. I this for right? Isn't it way too much for fishes to go through everyday?

So, I wanted to know what my alternatives were. Is it ok to add more sodium bicarbonate to elevate even further the pH and KH? This way, when CO2 turned on, I could achieve a 30 ppm CO2 concentration and a 1 point drop in pH.

Thank you!!!!

 

[a1Matt]

Welcome to UKAPS

My advice is to Ignore your KH and PH levels completely, and instead use a dropchecker with 4dkh water to measure your co2 levels.

If you want a more indepth answer as to why you should do that , then studying this article will help: viewtopic.php?f=34&t=467

 

[Tom]

Agreed with above

 

[Rafoda]

Ok, first of all, thank you

Second, I read (again) the entire article and still got some questions.
How can I just forget about pH if the article says: "The drop checker is nothing more than a pH test kit".
And how can I ignore my water's KH if I need it to cross with the pH to find out the CO2 levels?

Imagine if I ignore pH and KH and just care about CO2 concentration, I would get the tap water with 1KH, 6.8 pH. Then I insert CO2 until it reaches 30 ppm, and my pH drops to 6,3. That's way lower than the neutral pH I would like to maintain.

Thank you again!

 

[Tom]

Don't worry about the pH! The CO2 concentration is more important. If you use 4KH water in your drop checker with pH test kit, it won't matter at all what pH or KH your tank water is (within reason obviously). The fish really won't be all that bothered either.

 

[Rafoda]

So are you saying I shouldn't care if my guppies are in a 6 or 8 pH water? Almost every website has a acceptable pH range for each individual fish.

And when the article says that a one-point pH variation during the day is normal, what does "one-point" mean? 0.1 or 1.0?

Thank you!!!

 

[Tom]

Yep, they will state an acceptable pH but to be honest, fish will tolerate a pretty wide range of pHs. If you think about fish imports, if you measure the pH in a bag of 1000 guppies that come in from Singapore, it's a good bet it would be around 4 - 5.5. The problem comes when the pH swings too quickly, and many species are particularly susceptible to that and need extra time to acclimatise.

I would imagine they mean 0.1, but much bigger variations can be seen. Depends on the setup.

A fish (such as many South Americans and killifish that pretty much live in peat) may come from a river of pH 5.5, but hardly anyone is going to keep their system that low. You will more than likely find they are fine in much higher pHs.

Tom

 

[ceg4048]

So are you saying I shouldn't care if my guppies are in a 6 or 8 pH water?

That is correct. You should not care because pH due to CO2 is irrelevant. It depends on why your pH is at a certain value. This determines whether you need to be concerned or not. If, for example ammonia is being released into the aquarium, the pH would rise. But what do you think is doing the damage, the pH or the ammonia?

Water column pH is only a smoking gun. You must identify the reason that the pH has risen or fallen, then evaluate whether the phenomenon causing the pH change is a hazard or not. You must not get wrapped up in the pH number itself, because fish or plants do not really care about the actual value. If a toxic agent results in a pH change, then we need to worry about the toxic agent and to eliminate the origin of this agent.

Since we know that adding CO2 to water causes the rise of a very weak acid (called Carbonic acid), we don't worry about this occurrence because carbonic acid is not a hazard when it is external to the fish (i.e. it does not damage fins or gills or skin at the concentration levels we dose). Excessive CO2 kills fish and inverts by stopping their ability to expel CO2 from their bloodstream. This causes the pH of the fishes bloodstream to fall due to Carbonic acid in the bloodstream and that is fatal. In this case, the damage is done by CO2 internally, not by pH drop externally. Of course, if the CO2 level is excessive then the pH reading will be very low. So the pH level reflects the fact that there is excessive CO2.

Now suppose you add something like "pH Down". Did you realize that this is a highly toxic substance because it is made of a strong acid like Sulphuric Acid? This type of acid is so caustic that it is used to clear blocked toilets of debris! This is extremely toxic to fish, yet people very seldom ever worry about it. They just dump it in their tanks as if it were nothing.

So there is a difference in the components and substances that can enter a tank and that is what you need to be concerned about, not whether you measure this number or that number. Ph is a mirror to the dynamics of the tank. It is not, in-and-of-itself a cause for concern.

Almost every website has a acceptable pH range for each individual fish.

The websites themselves have no idea why the numbers are what they are. Someone captured a fish long ago in a river or stream and measured the pH of that river or stream. This pH value then became the "standard" for that fish, and people have been regurgitating this data ever since. The best that we can say is that "Fish xyz is typically found in waters of ph abc". This does not mean that the fish cannot tolerate pH values outside this range or that there are not the same fish in other waters of other ph values.

And when the article says that a one-point pH variation during the day is normal, what does "one-point" mean? 0.1 or 1.0?

One point, or one "Unit" means 1.0.
For your information, 0.1 is one tenth of a point. That means at night your tank could easily measure 6.2 pH at night when no CO2 is being injected and then measure 5.2 ph at the peak of CO2 saturation during the day. The actual pH value does not really matter. What does matter is whether or not the CO2 concentration level that generated that pH reading is too much for the fish.

Hope this clarifies.


Cheers,

 

[Rafoda]

Wow, thank you all so much for taking the time to clarify things for me.
I will definetely give it a try! I also bought a new timer today to start the CO2 a bit earlier and turn it off earlier too.
Again, thank you!!