I've tried all possible options.
vincent there are many ways to skin a cat, lets see if we can find better options for you to try
Firstly what pump is it thats causing all the issues and what l/hour does it pump?
Secondly is it controllable and or can ypou take it down to 50% of its opperation. Im assuming its not, but worth asking?
thirdly placement of the pump in the aquarium and where it blows against can have a strong influence and while i hear you when you say youve tried aløl options here, just have another look, its often the best way.
you can also 'choke' the pump back by wrapping some foam or a guard (like in nennie proofing a pump) to restrict its intake and thus lower its output.
these are just a few thoughts off the top of my head, there realy are alot of things one can do to use a pump. although by far the best is to have pumps on controllers which are not over powered for the tank and if a pump is just too powerful you may need to replace it with a smaller pump. too much flow can be detrimental to more than just your sand bed so you will need to read up and check that aspect as well.
sorry I am giving you more to think about rather than advice on what to do, but with the amount of info we have on the situation its all I can offer at the moment.