Tail Spot Blenny not looking so good....Help!

[Kimlafeiet]

Hi guys,
My new tank was cycled and ready, and I spent the weekend moving everything over. I moved my fish yesterday (2 occ clowns and the blenny), drip acclimated them for an hour. All seems well, everyone was doing great yesterday.
This morning, the blenny is REALLY pale (he pales overnight anyway, but not ever this much) and he was sitting in the front on the sand, fairly listless. He is never at the bottom of the tank, and he usually always stays close to his rocks.
My initial thoughts are PH swing. This tank has a glass lid, where my other tank was a totally open top (egg crate). Even though there is good surface aggitation with the tank, I have a feeling that glass top causes a major dip in PH overnight, which I have never tested for in the mornings or noticed without fish in it.
Unfortunately, I did not have time to test anything this am, as I was already running late for work. I took the glass top off, aimed my powerhead a little more at the surface and bolted out the door.
Is there anything more I can do at this point except wait it out? I am hoping to run home at lunch and check on him, but not sure I will get out of here.
What are the typical fish responses to ph swings (besides death)?

 

[Macscale]

How big is the tank?

 

[Kimlafeiet]

Ok guys....good news and bad news. Good news is Benny (the blenny) survived the possible PH drop, and was fine yesterday afternoon. Color was back, eating good, acting normal. Fast forward to this morning, glass lid off all night. I dont see him anywhere, but he is small and hides well, so I dont worry too much. Now it has been over 24 hours since I last him. He did not come out for feeding, which he has never missed a meal. I took apart the entire back chamber thinking maybe he jumped back there, no luck. I took apart my scape and checked every piece of rock, he is nowhere to be found. Checked the floor all around, behind, and under the tank stand.
He has totally disappeared. I have a sick feeling he went carpet surfing and one of my cats got a tasty treat. I hope he will just magically reappear tomorrow, but I dont think he will. He has never hidden away before like this.

Question though, worst case scenerio, he is deep in a rock dead......how do I keep my water params in check? I tested ammo tonight and we were not 0, but less than .25 with api test. I dont know if this is from a possible dead fish I cant find, or normal spike due to adding the fish this weekend. Did a 10% water change and dosed prime to be safe.
Poor Benny, I really hope he turns up.....I adore that goofy little guy.

 

[Kimlafeiet]

Still no blenny. Pretty sure he jumped and I may never find him