I think you have a female and a male. Look at the bottom of their tummies (don't you like the scientific nomenclature!). I always say that the female kind of looks like she has a beer gut, kind of like the number 5. The bottom of her tummy comes in close to a ninety degree angle. The male seahorse has a tummy that slopes down usually towards the tale. It's not a beer gut it's smoother.
If you can help it, don't use any chemicals in your tank. If it can kill one thing, it can probably harm others. I would start with less time with the lights on and more frequent water changes. You could also get a little macro of your own to grow in there to help with the water quality.
Don't stress about the ponies, relax and enjoy them. If you are unsure of something; ask first then do.