Algae eaters get along with almost anything except for goldfish and koi, but I'm not sure why. I'd recommend snails, they get along with EVERYTHING except plants...they do the same thing.
About a week ( I work at a pet store)
around 2 to 2 and a half years.
No, as long as the light is not too bright. If you get castle or something to put into the tank, then it can stay in there without being directly in the light
Only fish that are the same species can mate, so I dont' know what you mean by regular fish, but if they aren't the same species as the algae eater, they cannot mate. (That would be like a dog mating with a cat.)
That's a normal size for a plec,fresh water fish generally don't stop growing it's usually down to the type ie;comet or fantail etc.
If you go to Petco and look at the chart of what fish can be paired, you'll easily see that the Betta fish are incredibly aggressive. Just because they seem docile, doesn't mean they are. Why do you think they are quartered in separate containers? I would be cautious about what type of algae eater you get because depending on the type, they can grow up to be quite aggressive themselves. Plecostomus, sometimes commonly called "plecos," can grow up to 12" long quite quickly and will eat almost anything in the tank they think they can reasonably eat--- that might include your fish. Bottom feeding fish like Cory catfish usually stay quite small, are more docile, and do quite well in groups; unlike the pleco which is quite territorial and should be the only bottom feeder. An algae eating fish is, as always, not a substitute for regular aquatic maintenance. You must also feed your algae eater by purchasing bottom feeder wafers, as you cannot expect them to survive on scavenge alone. That might be what killed your fish, not the bettas.
Algae can grow back in as soon as 5 hrs.
Not Long. These different species of fish need totally different water temperatures and so should never be kept together. The Algea eater is a tropical fish and should never go below 70F. The goldfish are cold water fish and should be kept at around 55F to 65F. Applying the basic rule of all aquarists " 1 inch of fish needs a minimum of 1 gallon of water " you will see that the tank is far too small to accomodate even one goldfish properly so the life span of the goldfish depends on how often you change their water and how good the filter is.
No it will eat a bit of algae but it certainly won't be capable of cleaning the tank. The amount it eats will depend on how long it takes before the turtle kills/eats the algae eater.
Chinese Algae Eater.NOTE: they can get pretty long. and also the Albino Catfish can sometimes clean other fish.
No. Your tank is ridiculously overstocked. Your algae eater will eventually grow to the size of 12 inches long. Your mollies need more space. And your shrimp will soon die because of the polluted water from the overcrowded conditions.
1 hour
You rehome the Algae Eaters. Chinese Algae Eaters, what you have, are hardy tropical fish that turn increasingly predatory as they age. They will not stop sucking of slime coat of Goldfish or any other fish who holds still long enough. They are also capable of taking out eyeballs or even eating smaller fish entirely who sit still too long.