Bubbles on water surface

Bubbles, sometimes large and soap-bubbly looking, sometimes sea-foamy, began forming on the water surface of my axie's tank about two weeks ago. At the time, I believed this had something to do with the sand I had just added to the tank; however, the bubbles are still forming. They only appear once every few days, but it is enough to worry me.
The temperature in the tank is normally about 16 degrees C and the PH is 7.4. The tank has not finished cycling, so the ammonia is 5.0-7.0 ppm, the nitrate 5.0-10.0 ppm, and the nitrite 0.0 ppm. I do 20-25% water changes every day, and I completely changed the water the first time the bubbles appeared, yet I still see them. The sand was playground sand that I rinsed for two hours and left soaking in a bucket for two days afterwards. Are the bubbles something to do with the sand, part of the cycling process, or something entirely different/something I have missed?
I will post a picture the next time these bubbles form before I scoop them out.

Hi Boppo,

Gases can become trapped in the sand. When you clean your tank you need to stir the sand around to release any trapped gas.

Good Luck

Thanks for explaining what probably causes the bubbles. However, I still have a question; what do I do about these gases when they rise to the surface? Some of them develop a sea-foam consistency and stay in the tank for several days after I first spot them. I have been scooping them out of the water; is this the right thing to do, or is there something I should do or add to the water itself?

The bubbles / foam on the surface of the water can also indicate a high protein (waste) content in the water. The high Ammonia / Nitrite levels would support that as well. Keep up with the water changes and increase filtration till the water parameters test at zero (or a lot closer to it).