I think you can buy a set of brushes to clean things? Although I'm sure the others here will have some suggestions
Oh also, I was looking up the requirements for single tailed goldfish (as we are pretty much in the same boat!) -
40 gallons (48 US gallons, 180 litres) for the first fish with an extra 12 gallons (14 US gallons, 55 litres) for each extra fish. The tank needs to have a minimum length of 4 feet (120cm) to allow swimming room. Single tail goldfish are more suited to a pond when they are near full size to give them swimming room.
I thought it might help you out
As you could possibly try and get a 76 gallon, in that dollar per gallon sale, that way you could just save up an extra $36 dollars, rather than spend $40 on the tank now and then have to spend a further $75 later on to upgrade.
Of course, it's up to you, you know what you have space for, I just thought I'd suggest it