Is too much driftwood bad for water quality?

[irene]

Asking because I'm setting up a 75 for a pair of white crayfish I got and I'd like to put quite a few pieces of driftwood in there to provide cover.  I know it discolors the water, but does it actually harm fish or inverts?  I've also added some crushed coral to the filter for buffering and to increase the hardness a bit for them.

Irene

[BigDaddy]

In theory, too much driftwood could be a bad thing on its own.  Over time, and with few waterchanges, it would eventually make the water somewhat acidic.  This would, in turn, have a negative impact on the shells of your crayfish or other shelled inverts.

For example, my CO2 injected tank rarely has a problem with snails, as my pH of 5.8 quite quickly dissolves the shells of newborn pond snails.

Adding crushed coral is a good step to ensuring your pH remains high.  Just do some testing to ensure you have enough coral to offset the ph lowering tannins in the driftwood.

[woodendude]

I have 10 large pieces in a tank and other then lowering the ph and slightly discoloring the water I've never had any problems what so ever, the fish are happy and healthy. I also have a Blue Austrialian Lobster (crayfish) in this tank and he/she seems to be doing just fine.