Tank/Pond On Balcony

Hi to all,

For long I’ve been thinking to build modified my balcony into a floor tank/pond for keeping my goldfishes. This tank will take about half of the floor area. The tank size proposed to be 9ft x 3ft x 1 ft depth. The area will be exposed to afternoon sunlight (2-3 hours) also open for rain and falling leaves.

I’ve never build a proper fish pond, so I looking for advise and information to DIY concept. Should I put in lining/paint (for waterproofing) or just barely the cement floor?
Any special kind of cement/material for building pond?

Also to consider the type of filter for the tank; what is the best type and brand of filter for it. Need to consider the maintenance of the filter system, the easiest is preferred. Need information on the pros and cons of each type of filter system (for floor tank).

Input from all are welcome especially experience pond keeper.

Thank you.