Im sure this is a simple and very easy question. April 4th I will move up from my 65 gallon tank to a 150 gallon.

I want to keep all my fish, and some plants and my lava rocks my Emperor 400 and heater. I don't want to keep the same gravel.

I will do a water change maybe Wednesday instead of Monday.

When I get the new tank I will wash it out and inspect for leaks, wait for a little bit, then begin setting it up. I want to add the same water that I allready have (to save money on water and keep that same water that they are used too),I will probably add enough just to cover the gravel. I'll let that sit for a while. I will then continue adding water to the rest of the tank and get it too the correct temp. And then somewhere after 12-24 hours add the fish in.

Any advice.

They don't sell your type of filter in the UK so I had to look it up. It says it is rated up to 80 gallons which means you won't have enough filtration if this is the only filter you intend on using.

If you are swapping from one tank to another and one tank is already cycled, you can save yourself a lot of time and hassle by transferring the existing filter from the old tank to the new one. As long as you don't turn the filter for too long , you should be transferring a healthy biological filter. It's always a good idea to use as much water from the old tank if possible, then you can transfer the fish from one tank to another without any problems.

However, it seems that you don't have enough filtration for your 150 gallon tank so you may have to do get yourself either another filter to make up the difference, or get yourself a filter that will do the whole tank. Personally, I prefer the idea of using the existing biological filter, even though it isn't quite enough, it will certainly give you a head start.

i would just add the water from the old aquarium to the new one, top of with fresh water, add the filter and heater then the fish. i dont see the reason to wait for a day myself.
but your filtration like stated will have to be increased to accomidate the new tank size. the marineland hob are great filters for community tanks but are a little lacking for oscars imho. you should add another filter asap. i would recommend a canister filter that you can run independently or in conjuction with your hob

and having two filters is also benificial during cleaning.
you can clean one at a time (one week interval) to maintain
the cycle. moreover, you will have fall back when one unit
bug-down.

I guess I forgot to mention I have a FX5 siting in a box ready for the new tank this Saturday. Im going to use that with the Emperor 400. Also, Petsmart is giving away an ungravel filter with the tank and stand. I may use it, I just dont want all these cords and filtration to be seen in the tank.

Don't bother with the under-gravel filter... with messy fish like oscars, lots of crap get stuck down there... lol

problem is, cant sell it back to Petsmart... I can't ask them to take it off the final price of the setup. It supposed to come with it. My guessing is because the UGF was specifically built for ths Tank. The filter base is 24 x 24. I think it comes with two trays. All the other UGF's in Petsmart do not fit these specifications. Which means I need to figure out how to get rid of it. The measurements for the tank are as follows:

24w x 46L x 31h

Its a beast.

I believe I covered all the basic