Recently I've started noticing an oily film on the surface of my betta's tank. It's there as soon as I put fresh water in for a water change and just tends to build up until I do another water change. I try to skim off as much of it as I can periodically, but can't fully get rid of it. I just put the tank together a week and a half ago for a new betta, and the filmy stuff doesn't seem to be causing him any trouble thus far - he's very swimmy and eats like a little pig. Should I be concerned? Any suggestions for how to get rid of the film?
Tank info - 3 gallon unfiltered tank (it did come with a filter, but I didn't bother with it as I didn't think it was possible to hold a cycle in a tank this size). I keep it heated to about 80*F. I do a 100% water change once a week, using tap water and 4-5 drops of Prime per gallon. Just one betta in the tank, no other critters. Everything in the tank - gravel, silk plants, cave, etc. - was thoroughly rinsed with very hot water before it went in the tank.
I believe that oily film comes from the water conditioner, Prime....especially if too much is added. I've had it happen with both Prime and Seachem's Betta Basics water conditioner (with the Betta Basics, I ended up with not only the oily surface, but cloudiness and eventually what looked like dissolved tissue "fluff" accumulated at the bottom of the tank....ugh!).
Yeah I also use Prime and have used Betta Basics in the past, and the only time I get an oily film or scummy surface is if I turn my sponge filters off. Also, sometimes if I add in a new IAL it will develop a coating of slime for a couple of days before it sinks.
If you have filters operating, it may not be as noticeable. I have over twenty 2.5 gallon tanks (on some the filters are operating, some not...depending on the preferences of the fish inhabitants) and that's a LOT of water changes I do every week. I can say with 100% certainty that it is ONLY when I use the Seachem products that I get the oily film and sometimes, if I accidentally use too much Prime (or, in the case of the Betta Basics, use the suggested amount), I get the cloudiness and, when that settles, the white "fluff" in the water.
I used the Betta Basics only the once.....and when I had to redo all my water changes to get rid of the oil on the surface and the white debris that formed at the bottom of the tanks, I put it aside and have never tried it again. It is possible that I simply got a "bad batch", but I'm not going to buy another bottle of it just to find out. I've had 2 bottles of Prime.....and use it only if I run out of the Aqueon water treatment that I prefer. I know many people recommend it, which is why I bought those 2 bottles.....but what I've experienced with it and the Betta Basics makes me not much of a fan.