Yes buddy I’ll be using a small internal filter, this one is in line
Oase BioCompact 50
Unless you can advice more in an internal or sponge or hang on filter?
I bought that myself about 3 weeks ago and had to put a sponge filter in it that was already in use from another tank alongide until it got properly filled with the beneficial bacteria. I got lots of problems with nitrite/nitrate and even on one occasion got a green ammonia reading.
I did daily, even twice daily, water changes to try and resolve the issue. The sponge filter is only small but large enough to work the tank it was in so I was really miffed about the situation. The Oase filters clogged up very quickly every time and cleaning them was easier said than done.
There are 2 sections the filter. One has a normal sponge and the next has a finer sponge with activated carbon. The carbon bits were just getting absolutely gummed up in no time and although there were replacements in the purchased package, it seems a bit off if you have to change the carbon each time. I didn't of course as I washed them in tank water. Another thing is that one of the suckers has a mounting hole directly over the carbon filter section and every time I tried to slip the medium back into the filter body it pushed the sucker off.
I also increased the airflow through the sponge filter by joing the unused pipes from 3 outlets with normal Y junction joiners. That worked and the water readings quickly got back to normal. However I don't want the sponge in the tank for longer than I need, and I lost faith in the Oase.
In the end I just went online and bought an external filter. So much easier and even has a UV light. The change in the water was almost immediate. Although I didn't even think that the water clarity was in any way impaired, when I got the external filter running it was as if I had just had fresh new and completely transparent water, almost as if the fish were floating in the air.
Oh, The tank was fully cycled before this situation happened.
It's an Oase tank 50cm wide that has around 14 green neon tetras whcih I think are far better than the run of the mill Neon Tetras being brighter and smaller, then there's a single Santa Maria Endler, the other 3 having jumped out of the tank, and a pair of Scarlett Badis with a troop of 4 King Kong shrimp.
All of them are doing nicely together though the Badis tend to hide in a tunnel area in the wood behind the lower Anubia.
You can see them all happily going about their business from this link:
TheBridesMother - Twitch
I have CO2 for the tank as it's heavily planted. I used to do it the cheap way by using 2 x 2ltr coke bottles with citric acid in 1 of them and bicarb in the other. You'll have seen them going cheap on fleabay. They did a pretty good job but just looked $hite.
Not wanting to buy the ones that the professionals use at way over £100 each,
I opted for these and they are really good, really easy to use and smart looking as well. My 2nd arrives last Wednesday. They only took a couple of weeks to arrive as well.
I’m wanting to also co2 inject this tank and create a carpet for the tank, it will be a shrimp / chilli rasboras tank. 
