No. This is overcrowded and you change the water every day? That will stress the fish out and the constant change of chemicals and temperature can harm the fish. Please do not continue this. When a few die do not get more. I suggest change the water once every 1-2 weeks. Whatever you do, do not continue this.
You should consider getting at least a 20 gallon tank, or re-homing some of the fish to avoid overcrowding your fish.
20 guppies in 8 gallon.
The answer depends on the number of guppies. A few guppies can live in a 2.5 gallon tank or larger, temperature between 72 and 80 degrees Fahrenheit. Many people raise fancy guppies in 5.5 and 10 gallon tanks.
no
4,000
yes they can, depending on how many guppies you plan on getting.
No
Its not recommended to do that, but guppies are very hardy fish. So if you were to make sure not to over feed, and to clean the tank frequently, then yes you could keep 6 guppies in a 3 gallon tank.
NO! you will need at least 5 gallon for those
I would suggest upgrading to a 10 gallon tank.
yes
Guppies are very adaptable and small in size so a very large tank is not required for them to be happy in. A 20 gallon tank would be enough to keep five guppies in.
You do not say if the guppies are common guppies or fancy, also how many male and female guppies you have, yes as far as the snails and guppies go, one point to remember is the tank water should be above 72 degrees and some live floating plants for the guppies too hide in.