I have a bunch of pictures that I could submit here. I'd love to do more ID-ing myself, but I don't no where to start sometimes. I'll start with these two. From North Sulawesi a week ago. Being a former aquarium nut I take a lot of pictures(some pretty bad ones) just to have a record, so I can ID it later.  The first time I can remember being able to stump my guide with the little silver and black guy. I'm guessing its a juvenile and it dances like a juvenile Sweetlips. TIA

A site that I use to ID critters is https://www.inaturalist.org AI gives an initial identification and the community may jump in and treat you like a toddler until there is a consensus that, yes, that is a fish. I like to upload everything I shoot there. And some of the photos are pretty bad.

I think I got a hit for you on inaturalist.org:

 

https://www.inaturalist.org/observations/215075875

 

Striped Triplefin (Hecogramma striata)

Fishbase can be useful, I searched for Haemulidae (grunts) and narrowed to Indonesia and started looking at pics, you find the link to show species images and then click on the species and click on the pictures link above the the photo on the species Page.  I found this, it's white rather than silver however the patterns seem to match:

 

https://www.fishbase.se/photos/PicturesSummary.php?resultPage=3&ID=4465&what=species

Both suggestions are correct. Chris's link is actually one of my images of an early juvenile. You need about 5 pictures to show all the intermediate forms until it becomes the adult. There is also the closely related Digramma melanacrum which overlaps geographically with D. pictum and juvenile/young individuals can be hard to tell apart.

 

Both FishBase and iNaturalist are useful online resources to ID fish, the latter having the benefit of fellow underwater naturalists providing their input. I am working on a web portal about coastal fishes myself. At the moment is has just over 1000 species from the East Indies that you can view as 'illustrated checklists'. I will be diving about 6 months each year to cover the different regions of the East Indies and complement images with information about their identification, habitat preferences and behavior. But for now it is mostly images with identification and location. The site is now public on google cloud at biodives.com/aquanotes. An example of what the illustrated checklists look like is shown below for Dauin (Philippines). Click on the name of the species for higher resolution images and more details of the species sightings. This is also where more information about species will appear in the future.

 

Hi guys. Sorry I didn't see the responses until now. so it is a juvenile Sweetlips? 

 

Thanks, I'll have to try those sites for the picture to be ID a few days ago.