Cactus Dhalia

Pinch the side flower buds off to leave one flower bud for a bigger flower.
You can also pinch the tops off the plant to produce bushier plants.

I have lots of Dahlias T&T and i never pinch side buds off, its not necessary unless you are putting them forward for competition....if you have pinched the growing tips BEFORE the flower buds appear, then just let them flower and you'll gets lots of flowers...dead-head, feed and keep them well watered....yippee!!!

well ive left them for now and they seem to be doing really good although the one is suffering with blackfly,i keep spraying them off when ever i can with the hose but to no avail also is there a certain way to dead head them or just pull off dead flowers? oh and how do you split the tubers to expand sort of thing

Don't think splitting the tubors is done (don't know why). The way to propagate is in the spring - you put a tuber in a tray and water it and give it some sun and warmth and it produces all these tight shoots and you take those as cuttings.

As for the one with blackfly, make up some soapy water in a spray can and spray them wiht that - it works!

You don't need to remove anything from your plants - just deadhead them when the time comes.