Since you have a 5 gallon you are stuck with snails and shrimp as tankmates. However, algae eaters don't eat all algae. If you have blue-green algae then snails and shrimp work equally well. If you have hair algae then you would be better off with shrimp than snails but both would work. If you have brown algae or hard green algae then nothing eats that and you have to clean it off yourself. I think you are better off changing the tank's lighting then buying alage eaters. Especially if you can't recognize the type of algae in your tank and you don't want to increase your bioload.
If you aren't lighting you tank at all, find a bulb that is Daylight and rated for 5500-6500K depending on the plants you have. If you have the right light for your plants, they will get much bigger and out compete your algae for nutrients. Once your algae can't get nutrients faster than your plants the algae will die off. It will never go away comepletely but it won't take over your tank and plants.
If the bulb is Daylight but below 5500K that could explain the algae. Algae survive much better in little to no light compare to other plants and would "win" against your other plants for nutrients. So your tank would be over grown with algae. Since you plants aren't dead, I would suggest getting a bulb that is only 5500K if this idea is right.
If the bulb is Daylight and 5500-6500K then you may be leaving it on too long. I have that problem because I use a 5500K bulb because I like the way low light plants look. But algae loves low light which makes my tank a haven for algae if I leave the bulb on for more than 10 hours each day. If this idea is right, cut back your photo hours to only 8 hours a day.
If you have a Daylight bulb that is over 6500K then you may have a highlight bulb for medium to low light plants. I know some plants will have stunted growth and become a breeding ground for algae if they get too much light too long. If this idea is right, then cut the kelvins back to 6500K. I know there are 10000K bulbs out there, but you don't need much more than 6500K for most plants to thrive.
If none of my suggestions apply to your set up, then you may be stuck with algae. ^_^;
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