I would add that you can reduce the effect of natural and forced convection by changing characteristic lengths, temperature differences, flow characteristics, etc. It all depends on the case. Can you provide more detail on your specific case?
You can reduce by increasing the liquid volume and container surface area as this will increase the characteristic length (would recommend container rectangular geometry than circular geometry). if it is possible to put foam in your liquid, this will reduce the convection by half as this will significantly reduce the liquid heat currents.