DoubleDutch
Fish Gatherer
Magnolia leaves are great to use.I have been using Magnolia grandiflora leaves from my backyard for years now, but I have also used oak leaves for extended periods of time. Yes, what you want is dried out, old (brown) leaves, such as those naturally fallen to the ground.
In addition to tannin releasing benefits by the leaves, they have several other benefits. Some fish (cories, for instance), love to play between and under them. Some plecos love to rasp on them, becoming a source of probably both nutrition and entertainment. The picture below shows a magnolia leaf that has been in the tank for 1 week (right), the other a new one about to enter the tank. Shown is the result of busy bushynose plecos (x2), even though other foods are given to them.
I place several leaves in each of my tanks and replace them weekly or as needed (I look at them and decide). Fish appear to love them. Almond, Magnolia, Oak, Maple leaves, and almost certainly many others are all good so long as they are dried out (brown). Good luck!
View attachment 168667
I bake collected leaves in the oven to dry so I can store them in a bag.