Leopard Gecko Skin Darkening

[Silverlava]

I have had my two leopard geckos for a month now. One of them, Thor, has recently developed a darker color. (They're young, and still unsexed) It's a sort of black speckling seen in the yellow and white parts of his skin (pictures attached). Both geckos live in the same enclosure, a 20L aquarium. There are 3 dry hides (hot, middle, and cool) and one wet hide (middle). Daytime temp is 90 on the hot side and 80 on the cool side, and at night, it gets down to maybe 70 at most. Both are hand fed mealworms at about 9pm each night, and the cage has three small sources of water available at all times. The one with the skin darkening, we had trouble with getting him to eat at first. Now he seems to be eating great though, he'll eat as much as we give him. We figured he must have pretty terrible eyesight because unlike my other gecko, if you don't drop it within an inch of his nose, he won't go after it. I have not seen either of the geckos shed yet, so I don't know if this is what they look like going into shed. I've seen a lot of reptiles shed though, and it doesn't look like what Thor has. The other gecko, Loki, is a bit bigger than Thor, but since we hand feed them, they aren't competing for food, and I haven't observed any aggressive behavior. What does Thor have? Is he just growing into new colors? Before: After:

 

[Silverlava]

Sorry for the double, just saw that I should fill out this form:About your leo:
- Sex: Unknown
- Age & Weight: Unknown, young
- How long have you owned your leo: 1 month
- Where was he/she obtained: ++++++++

A) Health/History
- How often do you handle your leo: daily
- Is your leo acting any different today? No.
- Has he/she had any problems in the past? difficult to feed initially, but eats fine now.
B) Fecals
- Describe (look any different than normal) Just got him back from my boyfriend's who was watching them while I was on vacation, and he washed the carpet. So, unknown
- When was the last time he/she went: >24 hrs ago
C) Problem
- Please briefly describe the problem and how long it has been going on: See above post for description.

Housing:
A) Enclosure
- Size 20L aquarium
- Type (ex. glass tank): glass aquarium
- Type of substrate: reptile carpet
- Hides, how many, what kind: 3 dry, 1 moist
B) Heating
- Heat source: overhead heat lamp
- Cage temps (hot side, cool side) 90 on hot side, 80 on cool side
- Method of regulating heat source: check temp manually and turn off heat lamp if needed.
- What are you using to measure your temps: a thermometer
- Do you have any lights (describe): overhead heat lamp provides light during day, otherwise just ambient light.
C) Cage mates
- How many (males, females): 1 possibly male leo, still young and not sexed for sure.
- Describe health, or previous problems: no previous problems

Describe Diet:
A) Typical diet
- What you're feeding: mealworms, 4/day
- How are you feeding: hand fed
B) Supplements: never used
- What vitamin/minerals are you using: none
- What are you gut loading food with: nothing

 

[DrCarrotTail]

The darkening is most likely due to him getting older. Their colors change a lot as they grow and he may wind up having lots of spots all over. There are a couple recommendations I might make, however, and these could also contribute to his color darkening as well. First, I would recommend getting an under tank heater. If the air temperature on your warm side is 90 it may be too hot. They need a floor spot that's 90 to press their belly on to digest properly. If they don't have correct temperatures their color can become less vibrant. Also they really need a calcium and vitamin supplement. Their colors can darken if they begin to be deficient in vitamins and deficiencies can happen quickly as they grow and use a lot of nutrients. Without one you will have health problems in the future. The easiest supplement to use is probably Repashy Calcium Plus.