Oh ok, thanks!
So what I should do is turn it upside down, or insert the airline tubing from the bottom?
Thanks for the build up info, I was worried, do bettas do that because they are sick or something?
Pretty much just turn it upside down and get the water to enter the bottle byt the removed base of the bottle.
My step by step build.
Tools
Soldering iron to make holes
Scissors
equipment
500ml coke bottle
small internal filter that fits inside the bottle (motor and chord on top, sucks in water from the base that goes through a sponge then shoots the water out of the powerhead)
2 suction caps
Filter floss
Steps
1. Cut the base off the coke bottle you can make the ends serrated now or later.
2. I removed the powerhead from the filter and marked the size of the small fitting, then i made a mark matching that on the bottle and cut/melted a hole with the soldering iron.
3. Make 2 holes to fit suction caps opposite the powerhead hole. If the cut end of the bottle is not serrated yet then make it serrated now with the scissors or soldering iron.
4. Work out how much space will be left around the filter in the bottle and fill that with filter floss, attach the suction caps.
5. Poke the powerhead fitting through the hole you made from the outside then put the filter in the bottle and fit the powerhead back into it's socket. The powerhead holds the filter in place. Add some filter floss on top and cap it so the floss doesn't enter the tank.
If you can't fit the filter in the bottle then you will have to alter the design to run a tube from your filter or pump like this guy has on the linked video.
My DIY surface skimmer - YouTube