advice on how to go about introducing a new gecko to our resident gecko

Hi!
Juno is our resident female gecko. We are guessing that she is about 10 months old (got her from pet store last August). We would like to get her another female "friend." Currently Juno resides in a 10 gallon tank with the appropriate gecko set up (warm and cool sides, UTH, etc)

We are not interested in breeding, so we want to be sure that we get another female. We've been looking around and have found a few people selling their gecko along with the tank.

What is the best way to introduce the geckos (after we have purchased another)? One person has a 20 gallon tank with a customized enclosure and a 1 year old female. I assume that 20 gallons is okay for 2 geckos, but would I move Juno to that tank? If not, can I put the other gecko into Juno's 10 gallon tank after it has been used to 20?

What kinds of questions should I be asking of sellers to ensure that the new gecko will get along with Juno (or is that not a problem typically)

Thank you! We want to do the right thing by Juno, so any suggestions are greatly appreciated!

1. quarantine the new gecko from Juno for at least a month
2. thoroughly clean the larger enclosure and rearrange the "furniture"
3. Put both geckos in (assuming they're both adults and around the same size) and watch them carefully. Some tail waving or nipping is OK, as long as it subsides in awhile. Outrights attacks are not OK.
4. Observe them during the next few weeks to be sure that:
both geckos are eating
no one is losing weight or getting bitten or scratched up
no one is getting sat on all the time by the other one

If it works out, fine. If not, be prepared to keep them separately.

Aliza

Thank you Aliza! I keep them in their separate tanks for a month, but do I introduce them together outside of their habitats during that time? should I put the tanks side by side so that they see each other?

You want to keep them away from each other for a month as to make sure that the new gecko is healthy and okay. That means not even having the gecko tanks in the same room. Make sure not to mix any food bowls or water bowls and clean your hands very well after handling one of them. After the month is over and your new gecko is no longer stressed, eating, and is healthy. You can work on having them meet each other. The first few days you can place their tanks together so they can see each other through the glass. After about three or four days or them seeing each other I would take them out and place them in a large box together and watch their reaction. see how they do with each other. Do that for a day or two. The Third day you should clean whatever tank you will be using the house both of them in and wash is well. Make sure to start fresh. Set them both in the tank and keep an eye on them for that day. look for any injuries or wounds. If they seem they are chill and not showing too much interest in each other then you can leave them together for the night. Next day check them over and see how they are doing. If all is well then they will get along. But even after that day watch them close for a month or two for any signs of bullying. What I would do is weigh both geckos before you place them in the tank together. Keep a very close eye on their weight over the next month or so that they are together and make sure that no one is losing a lot of weight. Another big factor in housing leopard geckos together is their weight and size. You want to get leos that are around the same weight and size. weight I wouldn't go more than 10 grams off from each other. something to always keep in mind is that each leo has their own personality. Some female leopard geckos may not like being housed with any other leopard gecko. It really depends on your leo what will happen. You must be ready to be able to house them both in different cages if they don't fit well with each other. So keep that in mind.

Thank you again! great advice. We'll be sure to get a gecko with another tank just in case they girls don't work out.