Alkalinity Dropping

I got my water tested a week ago at my local Petsmart. The alkalinity came back perfect on that reading, same with PH.
Soon after I did a water change to remove nitrites and attempt to get my water less hard. Now its been a week since the water change. TodayI got my water tested again.
My alkalinity has severely dropped, but my PH seems stable for now. My alkalinity is currently at 20mg/L. I am super worried and don't quite understand how to get it back up. I'm guessing it has dropped because of the tap water I'm using for my water changes as both my other tanks have the same issue with low alkalinity.

I'm thinking of doing a rather large water change on all the tanks and replacing the water with "Betta water" from walmart. I'm guessing the betta water should help stabilize the alkalinity? I can't find much about the alkalinity of betta water on the internet though which worries me. Otherwise what do I do to help get my alkalinity where it needs to be? I don't understand why it dropped so drastically in the first place? Any suggestions? I have been using the same tap water (for filling the tank and water changes) since I started the tank almost six months ago and Ive never had this issue.

A little about my tank: 5.5 Gallons, Houses 1 betta. I do 10-20% weekly water changes. The tank has one plant: an Anubias frazeri. It is a heated tank staying at a consistent 78-80 degrees. It has a filter but it creates a current too strong for my fish so I only turn it on for a few hours after water changes.

Ive read that the plant could be contributing to the low alkalinity but I don't know enough about it to know weather this is true or not. Should I remove the plant?

Are there buffers for this I can buy? Does anyone recommend any specific buffers if so? I'm a little worried if I use a buffering product that the alkalinity will spike drastically and harm my fish.

If this is the wrong group to be posting this in please drop suggestions for a better place to post this, I am quiet new to this forum.

 

Hi, welcome to Fishlore

First off: Get the apI master test kit and the apI GH and KH test kit. The test strips can be astoundingly innacurate, so you need to get your own liquid ones.

Alkalinity, or KH is what causes the pH to change. The lower the alkalinity/KH, the more temperamental your pH will be.

If your pH clocked in between 6-8 there is generally no need to worry. If you have a betta they can probably go down to about 5.7.

If you are still worried about your KH, add a chunk of cuttlebone (in the birds aisle). This will bring it up.

 

Thank you!! That was extremely helpful! Is there a threat if the alkalinity were to get too high? I'm still trying to learn more about it. From what I've read it is a threat if it gets too high, but its a bigger issue if it gets too low. Is this true?

 

It would only be dangerous if it was above, say, 15.

 

Now that Discus-Tang covered up the alkalinity and test kit issue, I would like to clear up the filter issue.

Keeping the filter on for only a couple of hours every time you do a WC is like me turning on a reading light for a couple of minutes into reading a book.

I would keep the filter on 24/7.

If the flow is too much, you could try the water bottle baffle method.
You can find some videos on YouTube on how to make one.