large aptasia

[Navarchus]

If there is one thing you don’t want to do is play with aptasia!
Based on my experience, injecting stuff may look as solving things, but at the meter of fact it just making everything worst. Upon injecting, while the syringe needle in penetrating the aptasia it will feel in danger and immediately retract into holes in the rock then it will spread its larvae in to water currents in the aquarium. The next step will be the development of new colonies of these horrendous anemones.
FYI any remains of the aptasia body left attached to a rock or drifted in water current have a fairly good chance to regenerate into a full aptasia instead of eradicating you will cause proliferation.

So what should you do? Use a commercial product such as “Joe’s juice” or “aptasia X” by RedSea. With these products the aptasia is being feed with the stuff that kills it, since it see it as food, it won’t get frighten and die with its larvae.