Fuel issue

[Blu]

Ever since I got this Helix clone two years ago, I have this ongoing issue. Once in a while, the scoot will be starved of fuel, even the fuel filter is empty. I've been thinking all along there is something swimming in my tank and once in a while finds it's way to the outlet. It usually happens around half a tank, though the other day when it was cold and the tank was full it started to starve but cleared up before it died. So I'm wondering if it can be anything else. The auto choke seems to work fine, but maybe not, so I ordered one today. The only other thing I can think of is the diaphragm fuel pump. I have no experience with this type of fuel pump. So, to get to my question, can this fuel pump behave badly sometimes, but not often? I need to remove the fuel tank and wash it out, just haven't got to it. It looks clean inside, but there might be a fish swimming around in there. When it dies due to this (twice) I blow back through the fuel filter and it runs fine, but I don't know if I'm fixing it or it fixed itself.