You should never keep sharks like RTBS with other sharks or shark-shaped fish, as the RTBS grows it will become increasingly territorial and agressive (a lot of albino sharks are just albino rainbow sharks which have a similar tempermental temperment to RTBS as well), it will kill any other sharks it see's or fish similar in appearance or colouring to itself.
So you should choose now between either having the RTBS or the albino shark but not both as otherwise sooner or later (if they have not started already) they will start to constantly harrass/chase/fight each other until one of them dies.
Such sharks don't make ideal tankmates with gourami's but they can technically be kept wth them, but you should keep an eye on them none the less- make sure you give the gourami's plenty of healthy tall planting or floating plants and the sharks plenty of caves with lots of exits or sturdy piles of rocks or wood for them to hide under. They should be fine as they primarily occupy different levels of the tank, with the sharks being bottom to middle dwellers and the gourami's top to middle dwellers, but by providing them with the right habitat they should stay out of each others way.
Tetras vary a great deal in size and personality/temperment and keeping requirements, some are very agressive or nippy, while others are very peaceful- some are exceptionally hardy while others are very fragile etc. However almost all tetra's i know of shoal together in groups, and need to be kept in groups of at least 6+ of their own kind. Once you have some idea of what sort of tetra's you are interested, we can be of more help to you in advice about them.
I'm not sure if the your RTBS will become too territorial/agressive for spotted headstander fish as it matures though, how long is yours right now?
