Filter removing tannins?

[Shadey]

I use Indian Almond Leaves in my water for my bettas.... I soak the leaves in a bucket of water for my PWC, and it turns a nice tea color. But after a little while of being in the tank, the color fades to clear. My tank is a Fluval Edge. I took out both the carbon and ceramic parts of the filter, and am currently just using two sponges in the filter basket, and the pre-filter sponge on the intake. I'm still losing all my tannins. ;; Any ideas? Thanks!

 

[LPXnoob]

I have a top fin 10 gallon starter with a 30 gallon filter on it that stays a almost natural brown. I have a inch of dark soil under 1/4 inch of river pebbles. There is also 2 pieces of driftwood along with about 10 plants. I don't know why your edge wouldn't keep the color if my 3x over filtered tank is holding it.