I recently watched GW when Monty was planting up his pond. I seem to remember that the recommended way to plant in containers with specialist soil had been changed/updated, but I can't remember what the new advice is.
monty planted his up in pure gravel but i have always used basic loam soil from an area of the garden that has not had fertiliser added to it in recent years. I had a first class pond in my old garden using plain 3 ltr flower pots as containers ( saves on expensive planting baskets) with small1/2 cm slits cut in the sides, say 4 per pot and top them off with a layer of grit to stop the soil from being disturbed by fish rooting around in the tops.
I like mark have used "normal" flower pots with holes cut in the side with a saw for some of the more ... adventurous plants like Equisetum , as it can be just as spreading as its terrestrial relative and have found the normal pots keep it more confined than the pond basket. It just breaks out through the many holes !
I repotted a number of the more lush plants this spring and am giving the new advice of just pure grit / gravel a go. Though as i recall from GW water lillies are still planted in the aquatic compost as they need a bit more substence to get their roots into.
Aquatic compost has some goodness added in but not enough to cause an algal bloom, but this 'special loam' is expensive. I do what mark does use normal pots with slits in and low fertile soil from the garden where something big has grown which has soaked up all the nutrients. Here's how i pot up a marginal plant; fill the bottom with fine gravel about 1/4 of the pot then a 1/4 of soil or aquatic compost so the plant gets a boost when you first pot up, put your plant in making sure the base of the plant is just under the rim of the pot, if it isn't you need a bigger pot, then half way up the root ball fill again with soil or compost and after that the rest i fill with gravel right up to the top of the plant, this way the pot is heavy and wont fall over and the fish wont be interested in tampering with the soil