Can pests run wild in your tank? FYI
Generally one aiptasia is not reason to run in panic or nuke a rock.
Generally, if your tank does not have an oversupply of something a pest likes, it won't multiply that fast. This is important to understand.

Conversely, if something IS multiplying out of all reason, you have a deeper problem than the pest. Your tank is charged with way too much of something. It may be your skimmer is under-performing re your tank size. It may be...

My quirky, buzzing, cloud-making damsel showpiece...
I love damsels. My favorite tank is a damsel reef. I'm pretty good at it. I don't have nipped fins or the like---and one of the keys, I think, is, a) keep it to one of a kind and b) figure there's 'one ring to rule them all...' or, there will be a boss damsel, and some species are more apt than others to take that role.

My dark lord of the tank is actually a golden onespot dascyllus---size and shape about that of the smaller...

Household products or situations that can damage your tank
1. pesticides
2. ammonia- or petroleum-based glass cleaners
3. scented candles
4. carpet fresheners
5. paints, refinishers and other associated products like thinners and cleaners, including from hobby.
6. smoke, including heavy tobacco smoke
7. air fresheners
8. Lysol and other cleaners
9. antimicrobial or antibiotic sponges or cleaners or gloves
10. flea treatments...

Informational: Help, my fish are fighting...!!!
The old freshwater designations of aggressive and community don't work well as marine concepts.

Marine fish are almost all (including the oblivious-to-the-world mandarins) capable of killing another fish, under one of two conditions: lunch, and if your tank is too small to prevent encroachment on what a fish's biology informs his small brain is 'his' space, or his food supply.

In the ocean, one fish eats another,...

Recommended or a reef---level of 2 or less.
For a FOWLR tank or fish-only: less than 30.
For many inverts, the survival limit: under 40.
Fish survival limit---maybe 100, but it's not going to be happy.

Some things actually use up nitrate: clams, for instance, reduce nitrate, but have many other high-end life requirements, so don't dump some poor clam into a fish-only.
Some corals like elegance also appear to require a little, so zero is not good for them....