Upper diesel tank removal for cleaning?

[Whaup367]

I have some contamination in my upper diesel tank, under the port berth/seat (the lower one has some suspended discolouration but nothing "sludgy"). I thought to remove the tank and clean it thoroughly but am struggling to disconnect the outlet pipe.
I've removed the filler and breather hoses and the retaining straps and trim that physically hold it in place.
Anyone have any tips, please? The hose clamps are loose and the hose rotates on the outlet but won't slide off, nor do I seem to be able to slide the tank out, leaving the hose in situ. There isn't much space to move the tank fore&aft but even if I lift it and pull I don't seem to be able to get the tank to slide off the hose, any more than I can get the hose to slide off the tank!
Should I unscrew the couplings to the tail and/or valve? If so, what's the appropriate tool for the job, please? (I don't currently have a spanner that'll open to the 50mm or so necessary).
Thanks in advance!

 

[Plum]

I have some contamination in my upper diesel tank, under the port berth/seat (the lower one has some suspended discolouration but nothing "sludgy"). I thought to remove the tank and clean it thoroughly but am struggling to disconnect the outlet pipe.
I've removed the filler and breather hoses and the retaining straps and trim that physically hold it in place.
Anyone have any tips, please? The hose clamps are loose and the hose rotates on the outlet but won't slide off, nor do I seem to be able to slide the tank out, leaving the hose in situ. There isn't much space to move the tank fore&aft but even if I lift it and pull I don't seem to be able to get the tank to slide off the hose, any more than I can get the hose to slide off the tank!
Should I unscrew the couplings to the tail and/or valve? If so, what's the appropriate tool for the job, please? (I don't currently have a spanner that'll open to the 50mm or so necessary).
Thanks in advance!

I assume that is because there is a collar or barbs on the hose tail and the hose has gone a bit stiff with age. If you cut the hose off just before the hose tail in order to remove the tank then cut and discard the short piece left on, maybe there is just enough slack in the hose to fit when the tank goes back in. If the hose is VERY old, maybe just fit all new hose anyway? If the couplings/valve are all leak free, I would not touch them.