Hi and welcome to Frog Forum!

Water quality is critical to the health and well being of your frogs. It must be cleaned and conditioned properly. Contrary to popular belief, bottled water (spring, distilled, or otherwise) is not the best, simply because they do not have the proper chemistry that frogs require. The best water to use is from the tap. I have been keeping a variety of aquatic frog for years and use only tap water. The key is proper water conditioning - I recommend a product called Stress-Coat (available at any store selling tropical fish supplies). Use a strength of 1ml per gallon of water. I use a syringe to measure. The water can be used immediately. Make regular water changes, the temperature of the new water matches the tank water. The bubbles are probably created by your filtration system.