Anchor for 8' pontoon?

What size anchor do I need for my 8' foot pontoon, for river fishing?

i have had good luck with a 7 lb

depends on the flow and height of the river, but I also have had good luck with 5 - 10#s

I have a 10.5' toon (22inch diameter), and due to safety concerns I rarely anchor...

i normally just anchor up in the eddies and then fish the drifts from there