How Do I Match The Parameters Of My Water Changes?

I have had my reverse osmosis system for some time and haven't used it yet due to some complications from my faucet at home.
I decided tomorrow to try again with the setup but every time I try, I come up with a million questions.
I have an empty tank ready to go so I could honestly experiment to my heart's content but honestly finding out answers to my questions on here from people who probably already know, might save me some time

Anyway I stumbled onto Seachem's website and it says I should add in equilibrium to my ro water, dosing for the entire tank the first time I use it.
Link here:

which is fine, because I have an empty tank.
After that I would just dose the water I'm adding into the tank, aka my water changes. The website says to add the amount that would be needed for the new water to match the tanks parameters.
My question is, lets say my ph slowly goes down because of fish waste and such
Should I match my new water to the tank parameters that have changed slightly or to the parameters I started the tank with/ the parameters I want my tank to be?
for example I decide to start my tank with a PH of 7.5
My PH goes down to 7.3 over time
Should my water changes be dosed for a ph of 7.5 or 7.3?
If I did dose for 7.5 (lets say a 20% water change), Would this throw off the tank chemistry?

I hope some of this is making sense!

I am wondering because Currently I'm actually using gallons of water from the store. It is RO water, with some minerals in it. I purchased my ro system because I'm tired of lugging around gallons of water.
The gallons of water have Baking soda in them to maintain a PH of 7.
So now that I think about it, the tank that holds my fish started off with that water. Eventually my Ph went down to 6.8 instead of 7. but it now stays at 6.8. But when I do my water changes, obviously the gallons of water stay at a PH of 7. It has never caused me any problems and my PH stays at 6.8, even though I'm adding in a different PH. I'm actually not sure about the KH and GH of the gallons of water (I could always test it though).
With that logic, the ro water from my new system wouldnt be a problem either correct?
I'm not sure if creating my own ro water works the same as adding in premeasured, mineralized gallons of water.

Lastly I want to add some of my ro water from my new system into my old tank slowly, that way my fish gets use to it before going into the new tank with the new ro water. Would I match the parameters of the tank in use (6.8), or just stick with the parameters I want and slowly the tank will form to those? I'm worried it will throw the tank into wack somehow!

I know this is a lot of questions, and they are a little vague so I hope a few could be answered. Thank you for taking the time to read!

 

My question is, lets say my ph slowly goes down because of fish waste and such
Should I match my new water to the tank parameters that have changed slightly or to the parameters I started the tank with/ the parameters I want my tank to be?
for example I decide to start my tank with a PH of 7.5
My PH goes down to 7.3 over time
Should my water changes be dosed for a ph of 7.5 or 7.3?
If I did dose for 7.5 (lets say a 20% water change), Would this throw off the tank chemistry?

I personally would try for 7.3, but doing it at 7.5 probably wouldn't raise the PH by even 0.1 to 7.4
If in your actual situation the tank is 6.8 and the RO water is 7 I still would say the same thing about the PH changing, probably wouldn't even go to 6.9

Lastly I want to add some of my ro water from my new system into my old tank slowly, that way my fish gets use to it before going into the new tank with the new ro water. Would I match the parameters of the tank in use (6.8), or just stick with the parameters I want and slowly the tank will form to those? I'm worried it will throw the tank into wack somehow!

The different parameters will balance out, if you pour 5 gallons of PH 7 water into 5 gallon PH 8 water you should have 10 gallon of PH 7.5 water

 

You're fine. Let's calculate!
Let's say you have a 40 litre tank, with a 20% wc. That's 32 litres of tank water with pH 6.8. That equates to 10^-6.8 moles per liter, or 0.00000507 moles of H+ in total.
Mix this with 8 litres of pH 7 water (the wc). This is 0.0000008 moles of H+. Gives a total of 0.00000587 moles of H+, which in turn will produce a pH of 6.83.

I don't think a pH swing of 0.03 going to stress your fish

Unfortunately, nikm128 's last statement is incorrect.
If you mix 50/50 pH7 and pH8 water, the resulting pH is 7.26. pH is not a linear entity.

 

Maybe I should go brush up on my chemistry stuff.......

 

Maybe I should go brush up on my chemistry stuff.......

Haha don't sweat it. I deal with it every day, and if you don't, knowledge tends to get a bit rusty. I for one can't make a complete sentence anymore in French, and I took that class for five years...

 

Well, I feel like it would still be on topic, so would you care to remind me why/how PH isn't linear? Based on what you said I would assume that getting PH 7 water to 7.5, you would have to add an equal amount of water that's between 8.25 and 8.5? I'm thinking if 7+8=7.26, then 7+8.25 would be ~7.4 and 7+8.5 =~7.6. So you would want to add water that's ~8.3?

 

Did I miss when you said what type of aquarium do you have? Size, fish, planted or not, etc.

Equilibrium is good for adding Ca, Mg (fish need them), thus adjusting the GH. I would certainly add it to the RO water.

The pH, however, cannot be maintained with Equilibrium, the water needs KH for that. Without KH the pH will continue to drop until something will balance it - if you have wood, or certain substrates...

Baking soda will add KH to the water, but it can be exhausted pretty fast. While it is working, it will release CO2, which could be good for live plants. The Phosphate-based buffers are much more stable, but increasing the overall phosphates will cause algae growth. It is a big experience until you figure out it out for your particular situation.

 

Did I miss when you said what type of aquarium do you have? Size, fish, planted or not, etc.

Equilibrium is good for adding Ca, Mg (fish need them), thus adjusting the GH. I would certainly add it to the RO water.

The pH, however, cannot be maintained with Equilibrium, the water needs KH for that. Without KH the pH will continue to drop until something will balance it - if you have wood, or certain substrates...

Baking soda will add KH to the water, but it can be exhausted pretty fast. While it is working, it will release CO2, which could be good for live plants. The Phosphate-based buffers are much more stable, but increasing the overall phosphates will cause algae growth. It is a big experience until you figure out it out for your particular situation.

I believe they're just experimenting with the water chemistry right now, but I agree that something else will be needed for a stable PH such as seachem alkaline buffer

 

Well, first the why pH is logarithmic. If it wasn't, it would need a lot of digits to describe the whole range.

Example:
Lets say pH is linear. And pH 1 is pH1 in both scales. You get the following conversion (linear on the right, logarithmic on the left)
pH1 = pH1
pH2 = pH 10
pH3 = pH 100
..
..
pH13 = pH 1000000000000
pH14 = pH 10000000000000
This doesn't work very well.

The how:
pH is a measure for the concentration of the hydromium ion (H3O+ or H+) in water. There are some formulas how to convert the concentration to the pH:
pH = -log[H+] where the [H+] is the concentration in moles per litre.
The otherway around:
[H+] = 10^-pH

In perspective of your previous assumption:
-----Edit: something about the now deleted calculation didn't feel right somehow. I will redo it with actual pen and paper and post the result here-----

Know that any buffering and other contaminants in water will affect this calculation! Your buffer will reduce the effect. So in real life, the pH difference is probably (a lot) smaller.

Have a great day!

 

The alkaline buffer is carbonate-based, the alkaline regulator is phosphate-based - you have to decide which system is better for your case.

What are your tap water parameters? Why do you need to use RO water? The most successful fish keepers are adjusting their fish to the water they have, and not mess with chemicals.

Playing with the water chemistry is fun for couple of days, maybe weeks, then you start skipping... and problems will start... Unless you could invest in expensive monitoring and dosing devices, I would suggest to stick to your tap water...

 

I wanted to thank everyone for all the replies!! All of them were extraordinarily helpful!!! Please continue to be amazing and know that you really helped a fellow hobbyist out!!!!

 

Also to answer the question on the type of tank, I have one goldfish, and the new aquarium is a 40 gallon breeder. The old one is a 29 gallon which is too small since my goldfish is a comet. My family thinks I'm insane to go all out for one goldfish, but this goldfish has given me so much knowledge that I would have never had otherwise. Plus I get so much amusement throughout the day interacting with my buddy

I've tried tap water in my tank several times before and the first time I tried it, my fish was constantly seeking air at the top of the tank, for days. The second time I decided to try it, I found my goldfish's tail shredded in several spots the next day. Both times I did a small water change, probably about 20 percent and the rest being bottled water. The bottled water (which is ro) has never caused these issues in my fish. I used Prime in both cases but even after a few days, my fish would seek air at the top of the tank. I've tried it a few more times before and still never received good results. Reading my tap water with an aerator running after 24 hours of aeration resulted in the same parameters as just testing the tap right away. Both showed a ton of ammonia (I can't remember the exact amount but I remember being shocked) and my tank couldn't remove the ammonia even days later. I know a little ammonia is fine, but the amount in the tap water wasn't acceptable and for some reason my tank has never been able to remove all of it. A local fish shop near me uses ro water on all of his fish but I'm honestly not sure what the other pet stores use around me. I really have no idea why my tank can't process the ammonia, maybe its my filters, maybe its the size of the tank. But in the mean time my fish would be miserable with tap water. I don't want to make it harder on myself, trust me I don't! If I could use tap water I would, but I honestly have tried figuring it out and the only thing I could come up with is its too much ammonia. And every time I do a water change with tap, I'd just be putting more in. My municipal water source adds ammonia to the water. I live in a city so I assume that's why its so high. But I can't allow my fish to live out all of his days at the top of the tank due to the tap water. And like I said with bottled ro, I do not get that issue.

But I am so much more confident and excited to try my ro system again and do it right this time! now I know a lot more about it that I just wasn't finding anywhere online!!! THANK YOU!!!