Originally Posted by Nephelie
If i use real wood, i would be really careful with it. I probably gonna do more research into this and see how it is. Thanks for your thoughtful consideration.
Yeah, the reason i was thinking of real wood is because i know u can plant plants on it so that why i really like it. I probably gonna try it once my tank is like a few months old after it cycled.
What is tannin effects?
Wood, like all plant matter, decomposes once it is dead. Hard woods, of the reliable sort you would use in an aquarium (bought from a reputable fish store) has a very slow rate of decomposition. I have had wood in my tanks for years. Tannin (=tannic acid) occurs in most rainforest wood and it will leech into the water although usually very slowly once the wood is aged. At first, the tannins will stain the water yellowish to brownish, but after a few weeks I have never noticed any discolouration. This is completely harmless to fish. The amount of staining depends upon the type of wood. The light kind called Mopani wood tends to leech a lot in my experience, and it also floats so needs to be weighted down; I never use it. The darker wood like mangrove root (what I use because it looks more natural to me, is heavy, and very slow to decompose) takes a couple of weeks to leech out most of the stain and then it's fine.
Water in tropical rainforests that is heavily impregnated with tannins from a lot of decomposing wood and plant material is the colour of strong tea--clear but tinted. Scientists term this "blackwater" because it is so dark. It is completely harmless to all fish. As SinCrisis mentioned, some believe it is very beneficial to fish from such natural waters, like the South American cichlids, catfish and characins (tetras, pencilfish, hatchetfish). It will slightly lower pH, because it naturally softens and acidifys the water, but this is almost insignificant as SinCrisis noted.
You don't need to wait for cycling to add wood if you want some; it can go in at the beginning. It is in fact another surface the good bacteria will colonize. Here's a link to a good article on all this: http://www.sydneycichlid.com/aquarium-driftwood.htm