Odd Water Anomaly

Question
Hello! I recently added three small java ferns and a bit of java moss to my ten gallon fish tank, which houses one crowntail betta. Since I added the plants, I've noticed that the water has a sort of milky film across the top. I clean it off as best I can, but it keeps reappearing. My fish seems to be completely unaffected and healthy. I've tried using only pure spring water, as well as adding more treatment, but the film reappears after only a few days. I do a 75% water change weekly, and I changed the water before I added the plants. I have no idea what is causing this nasty film! Any advice would be very helpful. Thank you for your time!

Answer
Well this happens because their isn't enough water movement i would put a powerhead in the tank or a filter if you don't already have one. Once you have done what i told you tell me what the results are. With the water changes you only want to do weekly water changes of 25%.