ich or no ich that is the question !

[sade]

hey there im probably as new to this as possible and i need some help please.....
I have been given a 240l marine tank in this tank i have mixed live and non live rock ordinary marine sand, 2 clowns, small yellow tang and 2 yellow belly damsels. this tank has external filters which have been running for quite a long time when my friend got this 2 months ago she had to replace the water with all new from lfs and i think new tank has been an issue since. my damsels are flicking theyre bodies off the rocks but i can see no signs of ich yet and im curious to know (or hoping shoukd i say!) that there can be others reasons not so awful for them to scratch other than ich or velvet my water is very slowely improving last night it was as follows
ammonia... 0.25
nitrtite........0.5
nitrate........40
ph.............8.3

im doing small frequent water changes but other than that my only plan is too replace some of the media in the baskets bit by bit as they appear quite old

any ideas on the damsels flicking folks ?

[leebca]

Fish that 'flash' can be from any number of reasons, disease being the most likely. However, fish suffer gill damage when water quality isn't perfect for an extended period of time. There should be no signs of ammonia nor nitrites ever. These are both poisons that can irritate, shorten the life span, then kill marine fishes. Such poisonings and irritation cause fish to flash too.

Check the Internet for photos of fishes with Marine Ich and be on the lookout for signs of spots or any other symptoms that may help determine what is happening. In the meantime perform a huge water change (over 85%). Since it is large, follow these guidelines: How to Make a Successful Water Change

Start working on water quality. Since you inherited this system, you have a lot of catching up to do. Start reading. Learn first how to set up a system, even if you aren't do that, so you understand equipment needed and things that are needed to do: Setting Up a FOWLR Aquarium

Then learn more about water quality: What is Water Quality.

Since you face the possibility of Marine Ich, read this as soon as you can: Curing Fish of Marine Ich

Lastly, begin to familiarize yourself with the hobby by going through other posts you'll find in this convenient Table of Contents: Table/Contents - Link List

Don't assume the advice or information you've been given so far is accurate. Most of the time it isn't. You'll find the truth in the above posts.

If you find the fish act better after the water change, then water quality may be the issue. Post here if you need more info or help when and if you find other symptoms.