Hi Floyds mum
The most important thing (and probably the most difficult) is to get healthy otos from the lfs. Otos are different from most other fish in that they need a constant supply of food to survive. If this is interrupted for an extended period, as it often is between the time they are caught and the time they appear at the lfs, they will not be able to digest the food they eat later.
What you want to look for when you purchase them are ones that look plump and have rounded bellies. Only buy them from an lfs that you can trust and ask how long they have had them and if they are eating well. If they have had them for a week or more, are eating well, and look good, they will have the best chance of survival. Look the ones over carefully as they go into your bag and reject any you don't like. Buy a few extras, "just in case," and because they like to be kept in a group.
The do best in tanks that have been established for some time and have algae growing in them. Their diet can be supplemented with a good supply of zucchini, lettuce, kale, butternut squash and cucumbers. It helps to either blanch or freeze them first since this helps to break down the fiber in the vegetable. A good supply can be cut up and one time and stored in the freezer for easy use.
Good luck with them in the future.