Okay, I'm guessing here: if pupa are evident, then I don't think the queen is very far away. The queen is not very mobile, she just sits in place eating food brought to her by workers and laying eggs non-stop. The eggs are taken away by workers to nurseries where they hatch and the larvae are fed and cared for; logic would dictate that these nurseries would be in close proximity to the queen's location.
Once the larvae pupate, they are often moved around by the workers; this isn't a guess, it's very common to move a stone or log and find hundreds of pupae where there were none the day before. Immediately upon being revealed or disturbed, the workers begin snatching up pupae and rushing back into the depths of the nest with them. The workers seem to be moving the pupae to take advantage of optimum conditions of temperature and moisture to facilitate their development.
These pupae are what many people refer to as "eggs". Back when I was a kid, dried ant pupae were sold as turtle food and were labelled as "ant eggs".
So...if you are seeing workers moving pupae around in/on your sump or other areas near your aquarium, I'd bet serious money that the queen is very nearby. The ants are not schlepping those pupae into your house from a nest under the far corner of your detached garage; the eggs were laid and hatched, and the larvae raised, somewhere in the immediate vicinity.
TLDR: you have a bit-butt queen ant somewhere close to your tank/sump. She is an egg-producing machine that works non-stop. Trying to rid yourself of ants by killing the workers you see scurrying around does nothing to get rid of the nest; that queen has got to go. Expecting to solve an ant infestation by killing worker ants is like shovelling your driveway during a blizzard using a teaspoon. It's nothing but wasted feel-good effort.
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