I use Dynamite Fertilizer, its a 9 month Slow Release forumula with micros...Its safe and recommended for Containers and In ground fruit trees or any plant for that matter. They have several different forumulas, so you can pick which one is best for you and your plants. They sell some of them at H.Depot and Wally world.The yellow container is specifically for Citrus.

Here is a link that might be useful: Dynamite Plant Food

ok, i will have to check that out over the weekend, thank you for your help.