A pre-filter is always a good idea, less cleaning of that which follows.
Watercress can be put all around the edges (assuming rock edge that you can
tuck it under). It will do fine, your water isn't that still with that much flow.
I wouldn't use them, they are most likely sick due to poor water quality.
Did you buy test kits while you were there?
Bog: Marsh, stagnant acidic water.
Veggie filter: plants that water flows freely thru.
What color is it closest too? The 0 or the higher number? Forget the strips
and get Aquarium Pharmaceuticals kits. Be sure the ammonia test is the two
bottle one. http://www.thatpetplace.com or http://www.drsfostersmith.com ~ jan
See my ponds and filter design:
http://www.jjspond.us
~Keep 'em Wet!~
Tri-Cities WA Zone 7a
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