[Kleftiwallah]

This seems to be the most appropriate spot, but shift it if you feel otherwise.

I have aquired a domestic plastic water tank in which I intend to grow veggies, it is about 15 gallon capacity.  There is an open water delivery hole about 1 1/2" up from the base,  should I leave this as drainage or should I drill a few holes directly into the base covered with crocs?

 I have a couple of buckets of gravel to go in the bottom ensuring the drainage should remain open but will any water remaining below the exit hole in the base stagnate?

I look forward to hearing your knowledgeable answers.

Cheers,  Tony.

[JayG]

I think you've already answered your question - without a few drainage holes in the bottom, the water would certainly collect and stagnate up to the level of the existing outlet hole.

[Kleftiwallah]

Hello JayG, 
thanks for the confirmation, so it's out with the battery drill and hole cutter.

Cheers,  Tony.

[Growster...]

With those drainage holes, you'll have the perfect answer for carrots, as long as you stand them up high to deter carrot fly!

Ours have been fab this year, in buckets though, not a tank like you've got!