There are 10 gallon aquariums available online from private and commercial sellers. These are small enough to make delivery easy and more affordable than a large tank. For a cheap 10 gallon fish tank I would take a look at eBay or one of the online shops. The link in the resource list will take you to 10 gallon tanks currently selling on eBay.
That would be a standard 29 gallon aquarium
Yes, a 10 gallon aquarium would be sufficient for most terrestrial salamanders.
10 gallon if its only 2 inches and a 20 gallon for 4 inches
Yes. I have seen it in tanks as small as a 10 gallon tank.
right around 400#.... water is about 8# per gallon.
A small species of sunfish would likely be alright in a 50 gallon, however many species of sunfish get quite large, on the order of 8 to 10 inches long, and would be too large for a 50 gallon aquarium.
The rule of thumb is usually 1 inch of fish per gallon. You could have 1 10 inch fish or 10 1 inch fish
If you have a red tailed black shark that is in a small aquarium but you now need a bigger one, you can buy a cheap one through Amazon's UK website. You will be able to find a 50-gallon tank for him to go in.
2 I think.
It would not be wise to stack two 10 gallon aquariums together with one being upside down. If you add silicone to seal them together, you will not have any way to remove a portion of the aquarium to feed the fish or change the water.
Bettas should be kept at around 75F to 78F.
You can put one maybe 2 one-inch fishes in your one gallon aquarium