Answer: Aphids can be a real headache when they attack aquatic plants. Here are two options that have worked for me:
Lady Bugs. These hungry little darlings will eat their wait in aphids several times a day. They will not harm the fish or plants.
Diatomaceous Earth. This is a white powder that will kill most small crawling pests, including aphids. It will not
harm your pond life, and is carried by most greenhouse suppliers and nurseries.
I'm not sure what the growth is from your Zebra rush but I suspect it's part of the plant, not an insect. Remove it if it bothers you. If another appears, see if it is somehow attached to the plant or actually growing from the plant. It could be a seed pod, or it could be a root node - or it might just be some other floating debris.
Q&A Library Searching Tips