Please stop taking free fish from the petstore without doing research first. Unless your plans include buying a 30 gallon tank in the future, you need to take BOTH of them back to the petstore.
Kuhli loaches are hiders, they are expert hiders. They are also shoaling fish, which means they do best in groups of 5 or 6. If you keep a single one, you are doing no favors to that fish. Also, it will get to be 5 inches long. A 3 gallon tank is unacceptable for a kuhli loach. The people at the petstore should have checked with you about tank size before giving it to you, and you've now learned your lesson that pet stores are notoriously uninformed about their "product" (and don't be fooled, fish are products to sell for them).
As for the algae eater, there are 2 types - chinese and siamese. If it has a thick, solid black horizontal stripe it is a siamese algae eater. These are peaceful community fish that work well with bettas and loaches. If it has a dotted line down the center, it is a chinese algae eater. If it's chinese, remove it from your tank immediately. They are NOT peaceful fish, they are aggressive and will target bottom flat fish like loaches (they will often suck the mucus layer right off other fish, which will kill them).
THe bad news about the algae eater? At 1/2 inch, it DOES count. It still contributes a bio load, and your tank is simply not big enough for 3 fish of those sizes. And they'll only get bigger. Algae eaters are recommended to go in tanks with a minimum size of 48" long. Now go measure your 3 gallon. More bad news? Both types of algae eaters are shoaling fish, which again means they only do well in groups of 5 or more.
Take those fish back. Your petstore did you no favors. THey will get bigger, I promise you that much, and a 3 gallon tank is unfortunately only big enough for a single betta, with maybe a snail or some shrimp. But everything that you put in that tank does "count."