you could top the soil with medium sized pebbles and slowly sink the pots into the water. net off any particles that float free. plain garden soil works for me.

I left the plants in the pots they came in (under garden centre advice) and have weighted top with pebbles and placed onto stones inside the pot so they weren't too low in the water (pot is deep and care label suggested a low shelf level). I was told to repot in larger pots with aquatic soil next summer after they've had a year in situ. I'm wondering if they need a sunnier spot?

The green sludge - is it string algae? That you can pull out.

I would get the plants out of the small nursery pots and give them some room to get their roots in the water. I plant mine in gravel in large aquatic plant bags, but you can also find plastic baskets with holes designed for water plants - the roots will seek the water and come right through the holes. Some of my plants (like my dwarf cattails) are planted directly in the water - I just place them in the water (between another pot and the pond wall) and support them with a few rocks until the roots start to grow and they hold themselves up.

They do look like they need some nutrition - my container pond has a few goldfish in it which provide waste material which in turn feeds the plants. Maybe try a few fish. Or, if you have no fish in your pond, you could just add some plant food right to the water. But be aware that anything that feeds your plants will also feed the algae. Alternatively, you could make up a bucket of water with some Miracle-Gro (or other general plant food) and let the plants soak that up for a day or two.

The entire bottom should just be soil mixed with half sand. Also they need more sun. Full sun is best. That will solve your problem. They will grow like mad though then. It's not really going to be a pond in a pot though soon. That iris especially will totally 100 percent fill that small pot.

I think I'll be making some changes. I saw the idea in a magazine but admittedly have put in different plants to the ones in the article. If I add a soil/sand bottom should I be planting into it or keeping the plants in pots? The labels indicated a shallow shelf level so I've stood the pots on big stones in the pond pot.

Just plant right into the soil on the bottom after you add soil/sand mix to the entire thing. Take them all out of their pots. Take all the rocks out. Give it a little more sun, they will grow like crazy I promise. But those plants will overtake the entire thing. You could also then maybe add a little empty pot in the middle so the plants won't grow there and still have a little pool area. Maybe be neat to put a little fountain sprayer or something in there to keep a pond feel.

You know what Julia, it looks nice as it is. Don't get overwhelmed, leave it the way it is. The plants will be fine and grow in nicely since you have soil in the little pots anyway. Just don't let it freeze in the winter, put in garage and it will be fine.

Next year if you want to change it, do it then. Good Luck, and you have great plant choices.

I've read the same thing that having some fish there will help with the food cycle. Fish will help keep mosquito larvae and algae in check, and in turn, their wastes help lead to nutrition for the plants (with bacteria and other microbes playing a part).Otherwise, you can have other ways of giving some additional nutrition to the plants (think of an aquaponics system where either fish or other methods are used to help the plants along...it can't be just water).