One candy cane tetra should I stock other tetra's with it

I have a 20 gallon tank with a 4 fish currently and one of them is a candy cane tetra who is the last one alive and I have had this tank for 6 years and most of my tetras have started to die off- I have had these tetras for about 4 1/2 years- and now I only have this one tetra left. I have not be able to find anywhere near me that sells them and I was wondering anyone knew someone who was selling tetras in the Denver,CO area and if not would it be okay to stock my tank with other tetras or would this be a bad idea
P.S. This one tetra has lived alone for about 4 months and has been totally okay

 

Since he/she has been in your tank for 4 1/2 years and is likely comfortable even as his buddies passed away one by one I'd say don't worry about it. If you find more and want them then get 'em. I've had single "schooling" fish who also were fine.

What are the other 3 fish?

 

The three other fish are: yoyo loach, pearl gourami, and asian Siamese algae eater. and okay great would I be okay if I got a group of like 4 other tetras ?

 

Sure, other tetras of similar shape will likely get along well with your old timer and may perk him up a bit. Lemon tetra's would be nice.

 

okay thank you for letting me know and helping in answering my questions

 

You're welcome. Please let us know what you get and how it goes.

 

will do I plan on going to my local fish store this weekend

 

I ended up getting 6 black shirt tetras and they seem to be adjusting well to my tank and all the other fish seem to be doing good