GSP usually has a gray belly on the sides? (pic and video)

[kingkoopa]

I have a question about my GSP, King Koopa. I got him beginning of December 2010, so he's pretty new. I'm a fairly experienced fish keeper, though this is my first time with a brackish water tank and a puffer. Some quick info for your reference:

Tank: 15 gallons, with a cave, and enough few fake plants to cover most of the bottom, so lots of potential hiding places, no tank mates. Wish I could get a bigger tank, but I live in a SMALL apartment and do not have the space at all. =(
Water levels: Normal, 0 ammonia and nitrites, less than 20ppm nitrates, pH is at 7.5; I do 40% water changes weekly, and some occasional siphoning when I see dirt. I used Tetra SafeStart to establish the new tank before I brought him in.
Temperature: 80-82F
Salinity: 2 tbsp of Instant Ocean marine salt per 5 gallons
Food: Frozen live mysis shrimp, once a day. 2 fiddler crabs once a week so he has something hard to chomp on.

If I'm missing any basics, please let me know and I'll provide the info asap! Now for the lowdown: so my Koopa is a really sweet and healthy guy, but he was always pretty shy. In the LFS near me, I was drawn to him because he was the chunkiest guy in the GSP tank, but he was 80% of the time hiding under a rock. Now that he's in his own tank, he's been so much fun and loves exploring, especially weaving in and out of the heater suction cups. He doesn't spend his time hiding under a rock anymore, but he certainly is quite shy, drifting closer to me when I'm not looking and when I am, he drifts back to the far side. He has a really healthy appetite, finishing all his mysis shrimp and constantly scavenging the bottom to look for more, and really DESTROYING the crabs I give him as a teeth trimming treat. Here's a YouTube video of him I took yesterday so you can see:



Here's my problem. I know that a healthy puffer has a clear white belly, and when he's awake, his belly is CONSTANTLY gray. Not the middle part, but the sides, and some of the underbelly near the tail. You can see this clearly in the video. He was always like this, even in the LFS, and at the beginning I thought maybe it might be the stress of living in a tank with tons of other puffers crowding him, but it's been a month and he's always like this. The only time he isn't gray, is when he is asleep... then his belly is pure white, and when he wakes up it remains white for about 5 minutes then slowly darkens to gray. Here's a pic of him just waking up:



Is this normal? Could this be an indicator that he has a health problem I'm not aware of, or could it be stress? He doesn't show any other abnormal behavior aside from being more shy than most puffers I hear about. Any opinions/advice from the pros would certainly be appreciated!!

Another thing: is there any way to tell the age of a puffer? He's a larger one, all the other GSPs were an inch, and he might be 1.5 inches, and really round. Should I be feeding him (mysis shrimp) twice a day, once a day, or every other day? Thank you so much for all the help, and for reading this really long post! I am really in love with my little guy, and want all the help I can get. Thank you!!

[Pufferpunk]

I wouldn't worry too much about the belly. He looks very healthy & eats well. You do need to get a hydrometer & up the specific gravity of his tank. You also need to vary his diet more.

Here's some reading to get you started: library/puffers-in-focus/an-introductio ... d-puffers/
library/feeding/feeding-your-puffers/

[JRide]

Hmm...my old GSP (Nismo) actually did the opposite of what you are describing. He would have a white belly during the day and a dark belly while asleep/just waking up. Wondering what others have experienced as well.

Good looking Puffer btw!

[borgey]

In the video he does not seemed stressed at all. His tail is fanned out and not curled up or anything. He looks nice n round too so I would say you're good. And if Pufferpunk says you're OK then there is nothing to worrie about for sure. She's an expert at this stuff

[sevenyearnight]

My Pig Pig gets darker sides after he eats. After he takes a nap, and especially after he poops, he no longer displays the gray sides.

[kingkoopa]

Thank you so much to everyone! So glad to know it's not a cause for alarm. He's a cute and happy little guy and I'd like him to be as healthy as can be. =) Pufferpunk, I'm definitely going to switch out his food. I also forgot to mention he eats my betta's frozen live bloodworms sometimes, and really enjoys it too! Yesterday I dropped half of a raw mussel in there, and he eyed it curiously for a bit before attacking it. I had to pull it out early or else he would have exploded!

Just wondering, borgey said that a fanned out tail is a good sign... Is that always/usually a good indicator of a healthy puffer (aside from the usuals, like a healthy appetite, a belly that isn't permanently dark, and roundness)?

I'm really enjoying this puffer community, so happy it exists because I'm finding all the posts and articles so useful and everyone so friendly and helpful, thank you again!!