oops I forgot to answer the rest of the questions. I would do a 50% water change. What size tank is it? Instead of fake grass, add some prolifera and feather caulerpa. It helps withthe nitrates and the seahorses love it. It is a natural hitch for them and you don't have to clean it like fake plants. Seahorses that have lots of macros to hang out in tend to have more cirri. Plus it is fun to watch them hunt for pods in the macros. Try to remove any bristle worms that are in the tank. A FW dip of the LR should get them out. Depending on the size of the tank you can also get a canister filter. I have a fluval with a spraybar attachment on my 20g high juvi tank. More flow, yet spread out enough that the seahorses are not stressed or have problems swimming around. On my 75g I have a sump with a mag 9.5 return pump and a ASM G3 skimmer. On my 65g I had a sump with the same skimmer and return pump.

Research meds you should have onhand before you buy the seahorses. IF they get ill, they go downhill fast and you may not get them in time. Seahorse meds have to be ordered. It's not something you can pick up at the local LFS. Seahorsesource had a really good supply or meds. Always have spare 10g tank to use as a hospital tank. (walmart 10.00)

ok 3 post in a row is enough, lol. I'm done now. Can you tell I'm seahorse crazy?

Angie