I haven't had fish for many years, but when I did I had a lot of tanks. Whether the cleaning methods are the same, I don't know.

I always cleaned the tanks with kosher salt. Wet the tank and sprinkle course, kosher salt and use it to scrub the tank. Make sure it gets in all the corners. Then hose the whole thing out until clean.

Never use soap or anything like that. Salt will clean it.

Jane

I use baking soda to clean my aquarium. It gets the water deposits off the glass and rinses clean. Hydrogen Peroxide can also be used to disinfect an aquarium.

You should cycle your tank before adding fish. Having a cycled tank will help prevent fin rot, and is a lot easier to maintain then an uncycled tank. There are lots of tutorials out there on how to do a fishless cycle. It's easy, but does take a little time.

Once the tank is cycled you can add your fish. I have one Betta in my six gallon tank. You could probably add a snail or ghost shrimp too, if you wanted. It's not really big enough for much more then a single Betta, though.

If you decide to go with a Betta, make sure you have a heater for the tank as well. Like all Tropical fish, they need to be kept warm.

You can also use diluted bleach and rinse well. Get your fish from a healthy source too. I have guppies that I have kept forever. A ten gallon tank in my office with airstone and light only.... No filter or heater or feeding on weekends. I have same strain in a 29 gallon ya home but my daughter also has some in a one gallon in her room. I change all the water in that every couple of weeks. The fish even in there have reproduced a couple of generations and all fish in that little tank were born there. Don't try this with guppies bought at petco lol! Here is a photo of her little tank

I agree that such a small tank isn't suitable for more than a couple of small fish, and regular water changes are so important.

I recently sold a 65-gallon tank, and I used warm water and a plastic scrubbie to clean it. I didn't get off every trace of mineral deposit (it had been up and running for at least 10 years), but it looked pretty good.

It's also great to get a "sucker fish". I'm not sure of their real name but this is what they're commonly referred to because of the way the suck on the glass and the bottom of the tank. They feed on the algae and waste in the tank so they help to keep it clean are also a cool addition to your fish collection.

Uh, no, not for a 6 gallon tank - algae eaters can get over 10 inches. I honestly don't know what would fit in there - even a single betta do better with a minimum of 10 gallons.