betta tank has oily layer

My betta is in a well planted 20g tank with filter and heater, and I cycled the tank before he went in. He did have a snail in the tank but he got harrassed so now the betta is by himself. An oily layer on the surface of the water seems to form and im not sure what it is. If I change his water it seems to be gone for about a day and then comes back again.

Could it be the food? He has recently decided that he doesn't like pellets anymore so he gets freeze dried brine shrimp (plus the odd pellet just to see if he might give it a go). I try to remove all the uneaten food too.

Water parameters:

Temp: 26C (78-79F)
pH: 6.8-7
NH3: 0
Nitrites: 0
phosphates: (high?) 5.0 mg/L

 

the little filter agitates the surface of the water a bit, but maybe not enough? I've tried a few different ways of placing the filter so that i dont cause too much current for him (I read that they dont like current)

should I try a small aerator to get more water movement?

He doesnt seem sick at all, although hes a picky eater. It just gets to me when I go check on him and see this oily stuff in the water.

 

I got a 2.5 gal w/ 2 bettas and a divider of course. they've been living in this set up since my son was born about 9 months ago, i've never had a betta live that long. i've never tested the water, never changed the water (just top off). they seem very happy. you're right about them not liking the current. i get lil' bubbles on the top of water, maybe a lil' oily. it doesn't seem to bother the fish and i can't really tell cause the hood completely covers the top. my guess would be the food, not much you can do unless you switch. how often do you feed him?

also, it sounds a lil' mean but i'm kinda waiting for them to kick the bucket so I can convert to a nano reef.

 

He only gets fed once per day, used to give him 3-4 hikari betta biogold pellets but now he gets one pellet and some brine shrimp. Occasionally I'll give him some green pea when the goldfish are getting theirs and he seems to like that too.

Ive never had a betta before, he seems to be quite cluey about his surroundings and he's interesting to watch. I just took some pics of his tank and he was not happy about the camera flared up a lot...the tank is nothing special really, some ambulias, vals and some type of lily? I wanted tall plants to break up the current and to give him somewhere to build his bubble nest. Either way, it has to be better than that cup he was living in!

 

Hagan makes a little skimmer adapter to fit most filters to remove surface gunk.

 

I've used the Hagan surface skimmer before. It works will with canister filters. Especially if you replace evaporated water regularly.

 

that might be an idea...i'm going to try an aerator first since I have a spare pump and a little eheim bubble difuser that i can adjust for small bubbles...since hes not getting sick from it ill try a few things before going out and spending up big at the aquarium shop.

People look at you a little funny when you tell them you have a whole tank set up for one betta fish when you go out to get equipment for it. I've had people tell me that he will get scared and die because theres too much room in the tank and they only live in puddles...ive also been told its fine to keep males and females together..you would think people would know about the things they are selling to the public

 

You'd think they would.

If you don't use the skimmer, the air stone will help for sure.