Diamond Watchman Goby

[Maxj30]

I had a great Diamond Watchman Goby. Got him maybe 2 months ago and he sifted sand like nobodies business. Every now and again he would eat small pieces of krill that my Snowflake Eel wouldn't manage to eat. About 3-4 days ago I noticed some discoloration going on around his mouth it was a little red and I thought nothing of it maybe he sifted and got a cut. Today I arrived home and he was not doing great. The red was now much more noticeable and there was blue too redness along his sides became apparent too. Some odd behaviors that I noticed is that it would swim with its mouth wide open next to one of the damsels. I have never seen my eel bother it before and I don't suspect my eel to have harmed it while that could of been the case I doubt it. Working on doing some water tests and results will be up soon.
Below are some images to help, I'm asking for a possible reason this happened, or if anyone may know thanks! Sorry some photos are not properly rotated.
In a cup

On the counter

Where it laid last

Eels First bite (It's dead I've never seen my eel bite it but who knows maybe he did it. Hes been discolored for four days)

 

[ThRoewer]

This fish had for sure intestinal parasites. You can see it by the knife back that he lost a lot weight despite eating.

This is way too common with these sand sifting Valenciennea gobies. In fact you can safely assume that 99% of Valenciennea gobies have worms or other intestinal parasites.

Due to weight loss they often succumb to secondary or opportunistic infections.

If you want to keep them for more than a few weeks or months you need to "deworm" them thoroughly before adding them to your tank.
Besides a prophylactic treatment with Praziquantel (PraziPro) I would also add a course of Levamisol just to be sure.

 

[Maxj30]

Thankyou

Thankyou

Thanks for the great information. Glad someone was able to answer my question.Picked up a Spotted Watchman Goby I think he will be a great addition to my tank.