They're not quite so crazy about aphids, but what they spit out the kuhlis loaches scramble for. I have seen so many kinds of aphids since started inspecting the plants regularly to hand-pick! There are green ones that exactly match the hue of a tomato leaf- cannot see at all unless the light is against them- and paler lime-green ones, and darker blue-green ones, and dusky grey ones, and dull violet ones, and even fuzzy ones. But the other day I found some that really surprised me. I hit my asiatic lily plant with the lawn mower by accident (if it's still alive I'm moving the bulbs come fall) and went sadly to pick up the stem for compost.
As far as other pests and helpers go, I still haven't identified these tiny white slivers of things I find on my plants. They're not whitefly- those have a wedge-shape with rounded wing tips. These are literally white slivers, and I am pretty sure they are plant-sucking bugs because I often find them stuck on a leaf surface perpendicular- head attached to feed I think (can't quite see that, they are so small) and body in the air. Easy to remove with a damp finger, but now I dispose of them. Found that my fishes don't really eat them- either they are too small to notice, or they don't like the taste (the tetras really like to eat cabbage moth eggs, though!) Also, I think they foul the water.
I had noticed that when I collected aphids and other bugs and saved the container in fridge for a few days, it would start to turn yellowish (yuck). Thought it was from using tank water (already has some organics, so maybe made the insects start to spoil?) so the next few times I used fresh, dechlorinated water. Still yellowing. Then I kept the tiny white bugs and fuzzy aphids out, no more yellow water. Two reasons to toss.
On some plants that have a host spider, I find very few aphids now, so I don't check every leaf anymore, just put my head down on the ground and look up through the foliage to see if there's any pear-shaped bug dots against the light. Also I have a resident dragonfly! or two. I see it angling in quick short flights around the garden, and resting on the raised bed edge. Really glad for that hunter's help, too.