Spare parts can be bought for most of the better brands of filter. Check with a few pet shops.
Air bubbles will do nothing. What is needed is a filter.
A one gallon aquarium is very difficult to maintain, however it can be done with proper filtration. An under gravel filter however does not work for saltwater very well at all. If you only use large substrate then it can work with constant water changes. I have a one gallon aquarium for a bright green mantis shrimp that I run with a small internal filter. I take a small cup of water out of it and replace it with my hundred gallon every once in a while. Tank has been up and running for almost a year now with no problem.
That would be a standard 29 gallon aquarium
The best filter for a small aquarium would be a simple hang on the back filter (HOB), also known as power filters. Common models are the Penguin, Aquaclear, Whisper, Cascade, Liberty etc. They can be found at www.bigalsonline.com under Filters>Power Filters.
One goldfish requires at minimum a 20 gallon aquarium with a filter, and an air stone would be nice
You can put one maybe 2 one-inch fishes in your one gallon aquarium
72x24x24
Its all your choice, my friend. However, the bigger the aquarium, the better the ecosystem- so I'd go with the 40 gallon. I have a 40 gallon fishtank myself.
The rule of thumb for stocking levels in a freshwater aquarium is 1 inch of fish per gallon of aquarium. For instance, five 1" guppies in a 5 gallon tank, or ten 3 inch cichlids in a 30 gallon aquarium.
Roughly 8.5 lbs per gallon. You do the Math.
To have one fancy goldfish you need to start off with at least a 20 gallon aquarium kit. This kit will come with a filter, filter media, the tank, and likely some decor. You also need to buy a bottle of water conditioner, and some fish food so you can begin cycle your aquarium to prepare it for the fish.
1