There are many new types of filters, heaters, tank cleaners, air pumps, and light bulbs available now that were not available 20 years ago. With so many types and styles to choose from, sometimes it is hard to pick the best ones to use for your aquarium.
One of the best filters that we recommend is the canister filter. A good canister filter will have plenty of water flow, with a lot of activated carbon inside. Usually a canister will also have bio-beads and/or bio balls too. These are important as they add a lot of beneficial bacteria that helps break down ammonia, and nitrite. Then finally , there will be a good sponge filter that traps most of the dirt, and is easy to clean.
Should you not want to spend the money for a canister filter, the next filter we recommend is a hang on the back filter that has a high flow rate, a lot of activated carbon, a sponge or other mechanical cleaner, and bio beads, or a bio wheel. Any filter with a combination of these media, should be a good one.
Try to get a flow rate of at least 10 gallons per hour per gallon of aquarium water.
So if you have a 20 gallon tank, you would want a filter with a flow rate of 200 gal. per hour.
The least recommended filter is the one with just a slide in carbon cartridge by itself.
If it has a good cartridge with a bio wheel, that is not as bad, but just a cartridge by itself is not the best. They will maintain an aquarium, but just keep a light load of fish in it.
Keep in mind that if you are keeping tropical fresh or marine fish, that you should get a good heater. The submersible heaters tend to be better than the hang on the back ones.
A good temperature for tropical fish is 78 degrees, and goldfish and koi do not need heaters.