Golden Gecko color

Question
QUESTION: We have 2 male golden geckos in a 30 gallon tank with a bark substrate, a hiding tree, a hiding cave, a couple artificial plants/vines, a water bowl and some basking type rocks. The temp stays around 80-90 during the day, 70 or so at night. A incandescant bulb is the primary heat light, a flourescent light provides general light.

When we brought the geckos home a few weeks ago, they were almost translucent in color with the very gold color down their backs. They eat crickets every couple days (3-4 between them) and a bit of baby food (banana or mango) every 4-5 days.

My question...their color has gradually gotten very dark over the last week or so.  We've only had them for a couple weeks, but there is no longer a gold/translucent type coloring...they are more of a dark brown/black color with hints of gold on their backs.

What are we doing wrong? Or is this normal?

Thank you

ANSWER: Hello Claire,

Do you have an undertank heater for them?  They need heating 24/7.  Do you turn off the lights over night?  They do need it dark or just a blacklight if you want, but they do need an undertank heater on at all times.  They digest much better with belly heating.
They could also be getting ready to shed, as well.  That could be one thing.
What are you measuring the temps with?
Do you feed inside of the tank?  If so, I would take out the bark substrate.  They can accidentally ingest the bark & become impacted, so I recommend paper towels, or non adhesive shelf liner.  Plus, it is cleaner too.
On another note, unfortunately you will most likely have to put a divider in there as 2 males may fight & is going to cause undue stress.  
Everything else sounds fine.  

Tracie

---------- FOLLOW-UP ----------

QUESTION: Tracie,
Thanks so much for a quick reply.  
They do have a under tank heater that runs all day/night. The lights are on from roughly 7am-8pm each day.
There is a thermometer/hygrometer in the tank to keep up with temps and humidity.
I do feed in the tank...I will try the bark removal.

What type of divider would you suggest? Possibly Plexiglas? Would that create too small of a living area for the goldens?

Thanks again!!!

Answer
Hello Claire,

Great you have an undertank heater for them on 24/7.  I have a feeling that they are dark due to stress then.  
You can use Plexiglass but make sure & cover it with paper so they visually cannot see each other.  Males get aggressive.  So if they can't see each other it would be much better for them both.
You can just have the humidity up in their cave & hide.  That is where they need it most since that is usually where they shed.
Let me know how everything goes.

Tracie