Hi Paul.
Theres a few waters i know of with Tench in them locally.
Lifford Reservoir, theres lots of Tench in there up to around 8lb but it can be a rough place to fish alone, so i dont go there much, its inner city near a housing estate...
Smethwick west park, again lots of Tench in there, shallow soft bottomed park lake with Tincas to around 8lb again, but many more of lower weights...
Himley Hall Dudley, Big Tench (and VERY BIG Roach) can be hard to get on there in the summer, popular water, has got a few rules barbless hooks, no catapulting groundbait etc.
Leasowes park, not really a top Tench water but they arein there, good if you live near Halesowen, not so great if your based near Chelmsley wood.
If you know of anywhere that ive not mentioned please say, i am Birmingham based and i know a few others here are local too and they may also chip in with somewhere i have forgotten/didnt know about.
