It all comes down the whether you're bringing it across the border personally in your own vehicle, or whether it's coming over via courier/post office/broker.
The un-official general rule of thumb is a border guard will let you back into Canada with up to $200 of goods per person in the vehicle, even if it's only a couple hour trip. (This is my own personal observation and may just be a long running random coincidence).
I've brought over a lot of tank gear from my mail pickup place across the border. Vortech pumps, Apex controller, etc.
It helps when the whole family is in the vehicle
P.S. Always be honest and declare everything. Don't try to hide anything. Usually I just declare it in a lump sum and the border guards are usually good with that.