Welcome to the forums!
How big is your tank?
The albino rainbow are territorial and semi-aggressive who get about 6 inches and they need a lot of space. It will not be wise to put a betta in with one.
As far as the algae eater, I best to let you read it so you can understand better..
Siamese algae eater
This fish is a useful algae eater, eating thread algae and the brush algae ignored by other fish. They also eat planarians ( flatworms ) which can become a nuisance in the aquarium.
SAE can be slightly territorial with their own species so they are probably best kept either single or as a group of 5 or more in large tanks.
Unlike the Chinese Algae Eaters the Siamese Algae Eaters will eat lots of algae. The more common Chinese Algae Eater stops eating algae as it grows larger, becomes aggressive, and annoys other fish.
Minimum tank size for a pair of adult Siamese Algae Eaters is 100 liters (25 gallons). The aquarium should be long and have lots of living plants.
As they are not aggressive, they can be kept in any community tank big enough. Their active behavior might stress some sensitive species like dwarf cichlids and prevent them from spawning. They should not be kept with Red-tailed Sharks
(Epalzeorhynchus bicolor) (which yours is pretty much the same thing) unless the aquarium is large and well planted, because that species is very aggressive towards all its relatives.
A very hardy fish, it is easy to keep and feed, eating both algae and just about anything else put into the tank, such as flake food, pellets, live foods, parboiled vegetables, etc. It does a diligent job of removing algae from plants without harming them, as well as from decorations and aquarium glass. Considered by many aquarists as a necessity in any well-planted aquarium. Cover the tank carefully however, as these fish are strong jumpers.
SAE grows up to 6inches needs a well filtered oxygenated water with a pH around 7, temp in the higher 70s"
I don't believe either one will be good with a betta, nor are they good together. Unless you have something such as a 55 gal they are in.
Sorry Sena! I didn't finish reading all the posts (don't know why =( ), but you gave good info, sorry if I stepped on your toes!