I'm not a leo owner, so I can't give you advice, but why are you going back to Petco? Petstores will give you horrible advice. There are rare gems (very rare) that know what they are doing, but these huge chain stores do not hire for animal experience, and the corporate policy towards certain species care is criminal. 

Please, I'm sure there are some great leopard gecko forums, I'd recommend looking there. 

I think they meant to get feeders at petco, rather than advice, although I do agree with you Sapphire that petco advice is generally no good. 

How long have you had the leo and what/how much/how often are you feeding? Waxworms are very high-fat feeders so those may help, but they have low nutritional value and the geckos can get "addicted" to them so use sparingly. 

IN RESPONSE TO DARK

I feed him 7-9 mealworms every 2-3 days and let him eat when he wants. When the dish is empty I fill it back up. He is about 5 months old and like stated, it takes him 2-3 days to eat the 9 mealies. I also feed him crickets twice a week.

If he is loosing weight rapidly I's suspect parasites. Have a fecal culture done or give him a spot of panacur.

I've heard several people recently who work at these chain stores, people usually take these animals back and dump them there, so I was hoping that wasn't what the OP was doing.

Fecal culture is definitely a great idea. 

Shellboa is spot on. If it's dratically losing weight expect the worse.

If it's "graduallly" losing weight just try bumping up the food and calcium.

In response to comments about parasites...

Though i did not buy him i know he was bought from a mainstream pet store such as petco. I WAS NOT BRINGING HIM BACK. But going to buy stuff and wanted to know if there was anything i could buy him there. Could he have aparasite from the store where he was bought? I say this because i know the breeders that they get there animals from do not follow all the neccecary precautions. Also, i was just told that a few days ago a family member dropeed him but only about 4 inches.They said he landed on his food dish half way, on his stomach. Could this be why? Also, I am going back to petco again to buy dog stuff. So is there ANYTHING i can buy for him there.

Not really anything you can get, no. 

Reptiles, whether captive bred or yanked from the wild, can have parasites, unless actively treated for them. Its normal for them in the wild, but in captivity, they can't get away from their poop, which has the parasite eggs in it. They constantly get reinfected. Large chain stores still buy wild animals instead of buying them all captive bred, so cross-contamination is to be expected when buying animals there. Many people who buy animals from the large chain stores have them die after not too long.

Because of the way that these stores just seem to buy wild animals, I couldn't say much about what they buy from breeders. The breeders that decided to offload their extras *could* have had healthy animals, that simply got infected with parasites on site. Seeing as these stores refuse to give customers information (usually) about where these animals came from (most times even the workers dont know!), saying the breeders don't take precautions is an assumption.

Parasites like MITES can also burrow into the substrates kept in that section, so when you buy substrate from those stores you need to heat treat it, or you could get surprise mites...this actually happens a lot.

Treating for parasites is usually easy, but you will need to get a fecal test done, or your vet will not know which medication(s) to treat your animal with. You REALLY need a vet trip, especially with the rapid weight loss.
Do you have a calcium dish out?
There is really not much you can get for reptiles at those kind of stores other than the very basics, and dishes. However, if you want advice on what to get, and where to get it, we can easily answer those questions.

+1 calcium dish.

How "rapid" is the weight loss or is it just gradual?

How does the gecko look in relation to the picture you posted from the 15th?

And does his poop look normal?  Or is it runny?

I'd say that almost anything can be bought online cheaper. Amazon has a ton of herp stuff. Big Apple Herp and LLL Reptiles also (although I would NEVER get an animal from LLL, sometimes their supply prices are really, really low compared to others).

good luck with your gecko. I don't have anything to add here, except that it might be nice to get a rundown of husbandry details?

and if someone dropped him 4 days ago, and he's lost significant weight in that 4 days, you have a much bigger problem and I'd consider it an emergency that needs vet attention asap. 

if he's been losing weight for some time and it's just now becoming noticeable, it's a problem but maybe not such an emergency.

so: details. what size cage? how many hides, and how situated? pictures would be VERY helpful. what are you temperatures in the hot side, cool side, and basking location? how do you measure them, and what are you using to heat? are you dusting your feeders, and if so with what?

how old is he, and how long have you had him? the more detail you can give us, the better able we are to help. 

Great questions Aimee!

wait - I went back and read again. he's 5 months old, but you didn't buy him? I'm a little confused. please elaborate. 

thanks, KG - something like this can be as simple as being a little cold for good digestion, or the cage being in a noisy place that stresses the gecko out. I always hope for the easy fix first.

In reponse to all of the people asking questions:

I didnt buy him, my neighbor had him since last December(Christmas Gift For Son). The person who previously had him did not care for him properly(They had 1 hide and no heat lamps). They also did not want it anymore. They were gonna bring it to petco, but petco has been know to actually THROW AWAY pets that are brought back. Due to this i offered to take him. Even though I am not perfect at caring for geckos, i have had them in the past with sucess.

Also, I think i was overreacting, his tail is not as thin as I thought it was.

Before anyone starts yelling at me for the cage setup, I just cleaned the cage today so his cool hide, moist hide mealworm dish, and other "cage stuff" is still drying.

Also, can geckos ever smell? Before cleaning the cage, it smelled slighlty, but i think that was the cage NOT the gecko itself.

Also, where can i get the more advanced care products for geckos such as basic medicinal care and stuff.Like SapphireTigress said, they dont sell that stuff at the mainstream stores. 

Lastly, is is ok that i know use a modified storag tub to care for him, i had a 10 gallon aquarium, but i didnt see the purpose of buyin a 20 gallon one day, when i can give him 3-4 times the space for a quarter the cost.

General Tank Facts:

DAY TIME TEMPS:
hot side - 85                                                                                                                                                                                                                                               cool side - 75                                                                                                                                                                                                                                               basking spot - 88

NIGHT TIME TEMPS                                                                                                                                                                                                                                 hot side - 80                                                                                                                                                                                                                                               cool side - 72                                                                                                                                                                                                                                             basking spot - 84

HIDES:
3 hides, one warm, one cool, one moist

DISHES:                                                                                                                                                                                                                                                     one mealworm dish, one water dish

FOOD:                                                                                                                                                                                                                                                         Mealworm dish is fill with 10 worms, and I let it eat when it wants, then refill immediatley. I also feed crickets 2-3 times a week. ALL FOOD IS DUSTED WITH REPASHY LEOPARD GECKO CALCIUM PLUS 

PHOTOS OF THE CAGE AND GECKO ARE IN MY PHOTOS. THE LID OF THE CAGE OF MOSTLY SCREEN. 

Perfect, that is exactly the kind of hting we need to know! YES you can use a plastic bin for termporary housing, I can't say for geckos but I know for snakes you can keep them well in tubs. I have also kept bluey tongued skinks in quarantine in modified huge plastic tubs, and its great for QT. Bean farm for some stuff, and this site seems to have a lot of medication options.  http://www.beardeddragon.co/index.php?route=product/category&path=60

You can also find some good steals on some items you maybe wouldn't think to look for on Amazon. :D

i was thinking aout keeping him in here for a permanent cage. It would be like a "gecko rack", which almost every person online who has more than a few geckos uses, but only with 1 tub. Since using the tub, my temp range has been better, and my basking spot is actually getting hot.(In the 10 gallon aquarium the heat lamp was too far away form the rock)

What are you using as a heat source?  You mention a heat lamp above, and lights can stress geckos.  Some leos don't even like the red lamps.  Most people use a belly heat source, like a heat pad, regulated with a thermostat (either a dimmer or one with a temperature probe/setting).  You didn't mention how you're measuring the temps, but I highly recommend getting a reptile temp gun if you don't have one.  I use one to make sure my gecko's warm hide floor is always around 90 F for good digestion.

Besides that, the setup sounds fine to me.  I agree with the comments above that if he continues losing weight, you should get a fecal parasite test done by a vet.  It sounds like you're offerring him all he can eat with proper supplementation.

I am unable to use a heat amt, since the tank is on a wooden table. Instead, I use a white daytim light and black nightime light. Both of these create a basking spot that is aroun 88-90 during the day and 85ish at night. It also keeps the air temp of the tank right. To measure the temps i use 2 termometers one on each side.

You can use a heat mat if it is controlled by a thermostat or dimmer...like EVERY heat source should be...paper doesnt burn until 451*F (this has come up a lot lately)...if your heat source is that high...you have more serious problems.
Many racks are made from wood, with no issues.

How are you measuring your temps? Stick on's are worse than useless, digital probes, such as the "accu-rite" are better but not by a lot...Infra Red temp gun is a necessity for any exotics keeper IMO. 

i am using temp gages, not stick ons

can a heat mat be used on a plastic bin? I dont wanna put my gecko back in it's old cage. It has alot more space now

Yes, a heat mat can be used on a plastic bin, with the same parameters as listed for wood (aka heat control).
Reptile Kid: What TYPE of temp gages? Details are very important, remember, we can't see your setup :D 

they are mechanical temperature gauges as shown here:

http://www.thatpetplace.com/analog-reptile-thermometer?gdftrk=gdfV2226_a_7c268_a_7c6967_a_7c204520

Are there any cheaper thermostats, i want to get one but they all cost like 100 dollars

yes, there are the a-lifes, which are about 30.
You need to replace your thermometer ASAP...those are analog, which are terrible. I'm telling you, you won't regret a $30 temp gun... 

This is a great how to for leopard geckos.   http://www.youtube.com/watch?v=72FaNhwxrME&list=UUCGLzU6yF7DBAIg0493j9ow

(but dont leave crickets in tank...)

Hydrofarm is another low-cost thermostat brand that people have used without issue.  You can find those on Amazon for ~$33.

My concern i the heat mat melting the bin? The heat mats attatch directly to the bin, and I think they will be too hot.

My concern i the heat mat melting the bin? The heat mats attatch directly to the bin, and I think they will be too hot.

I keep seeing these reheostat thermosgtats for around 20 dollars. Is this good

with the heat mat, how much of the tank should it cover

I don't cover more than a quarter or a third... You have to have a cool zone as well... So that you will place the heat source on one side and no heat on the other side thus creating a gradient from hot to cool... 

Zilla makes a thermostat also... Not sure how good it is... it's like $30 or so...Don't have one... Have a friend that has one.. and they seem to like it... 

As far as melting the tub... the potential is there but if you take all the necessary precautions you should be safer... Safer... But there is always a risk... 

Rheostats... Everyone is going to say stay away... They do have their uses but are more limited.  They work by controlling the amount of current that passes through the heating pad... Max current equals max heat.  Little current less heat.... Just like if you have a dimmer on a lamp... My opinion is this... Is you have a constant ambient temperature... It can work... If your room never fluctuates temperatures... The problem with Rstats is that the temp fluctuates as the ambient room temperature changes... You aren't controlling temperature... So in the event your AC shuts off you can hand temperatures that go beyond a safe range... Like I said... Has it's applications... with some Tstats costing only $30 bucks better to go with those.

Oh... And after thought... I like to plug the best source in without tstat and find the max temperature... That's just me though... That way you know what you are dealing with should the Tstat fail in the on position...

Blah...

Oh... And after thought... I like to plug the heat source in without tstat and find the max temperature... That's just me though... That way you know what you are dealing with should the Tstat fail in the on position...

Is a heat mat required though? I know most people suggest them, but with lamps, i have a god gradient, and a basking spot with good belly heat. It would be a waste to me to now go out and buy a hat mat when i havbe spent over 70 dollars on heating supplies.

Well... How about a ceramic emitter?  Reason is that for the most part they are nocturnal... You don't want light at night... A light is a light no matter what kind of light it is... An emitter would work... And if not... Then stick with what you have... If your budget doesn't allow for changes now but strongly consider upgrading in the future. I'm sure someone out there is using the same set up.... I have to go look at the pictures....

I have a zilla from when i started, it works just fine. I prefer the more expensive tstats, but the $30 ones work fine, especially for the OP's needs.

Its unfortunate that you spent money already for supplies that may work "ok", but if you want to do it right, you need to open your mind to other alternatives. You can always try and sell the equipment you dont need. I'm sorry, but I really feel that if you dont want to risk killing your animal and burning down your house...you NEED to have any heat source you use on a thermostat or dimmer(minimum!).  You don't keep animals for free...its going to cost money to care for it, feed it, house it, and heat it. If you don't want to get the necessary safety tools, you may want to find it an experienced home.

If you are heating correctly: paper shouldn't burn, wood shouldnt burn, plastic shouldn't burn. If you are experiencing melting or burning...either SOMETHING IS horribly WRONG, OR you chose not to use heat control. FIRES HAPPEN TO THE BEST OF US...Why tempt fate? 

Nothing is burning at all. I said that I am concerned that if I do use a heat mat, the wooden table I keep my take in will burn.

tank not take

if it will hurt your table, it will hurt your gecko. a thermostat will be your friend here. you could also consider putting another material between the table and the heat mat as a buffer, but seriously, the gecko will burn before your table does.

But the thing is, i am getting a GOOD basking spot with tons of heat. I BOUGHT AN IR TEMP GUN TODAY. And I will soon be getting a thermostat for the tank. The real reason i dont want to switch to a heat mat is i am already getting the required heat and temo range with lamps. until i do get a thermostat, my te,ps are checked a few times a day. Also i have heard that geckos cant see the red light. This is what i now use for nightime.

The basking spt is like 88-90 and the other temps are labeled above.

geckos can see any light, no matter the color, and can be stressed out by the oscillations put off by the waves of light if you're not using reptile-specific bulbs. this is especially an issue at night (this comes from a board-certified exotic vet who spoke at my herp society a couple of years ago). 

at the end of the day, you'll choose to heat him as you wish, but I would not leave any night light on a nocturnal gecko, period.

have you considered a small CHE for 24/7 heat in addition with your other bulb for the daytime bump they need for basking?  I've seen several Leo people suggest you have to have belly heat for proper digestion, but I've seen people use CHEs in combination with daytime bulbs have healthy and happy geckos.

I think i am going to get a very low watt che(like 40 watt) for nighttime temps, and during the day i will stick to my day bulb. Everyone is stressing that i use a heat mat so that the gecko also gets belly heat. He is still getting belly heat using the bulbs. If i decide to get more reptiles(I probably will), and change to a rack system, i will use flexxwatt heat tape. Before i close this post, is there really ANY purpose for a heat mat. If it is not 100% required i would prefer to stick to my setup. If not, i will change as it is whats best for my gecko. I am also getting a thermostat soon.

I think you're fine. as long as he's eating and pooping regularly and his hot spot is warm enough, he'll digest fine. just put the CHE over something like a slab of tile or rock that will absorb heat when he's not on it, too :)  

Where can i get tile that is safe for geckos? I was thinking about covering the warm side of the tank with tile for heat absorption

slate from the hardware store is just fine.

I still don't see that the geckos tail is that thin to be honest... I looked at the picture a few times and did again just now... could it be that it was young and looked bigger in relation to the size of the body and now the body is growing and the tail appears smaller?  I mean if you go search leopard geckos online you see all sizes of tails... I mean in the one picture all I notice is that the water dish is empty.. lmao... 

So like whoever said it above, if it's eating and pooping then things are good... I'll say it again the tail doesn't look that small... 

I'll now go out on a limb and say that I don't provide a basking spot for my leos... and I won't unless I see they start experiencing problems... They are in a room where it's almost always 80°.  I have a water dish and a branchy hollow thing for a hide...  I keep them on paper towels and they do have a light.. an LED that stays on during the day... that's when they hide in the loggy thing... then there are dim blue LED's that we keep on at night... kind of like moon light.  They are active alert and run around when there is food around and don't do much during the day.  Their poop is good and they have great appetites... I've kept them like that since day 1 and no issues... I keep them on a diet of crickets., superworms and discoid roaches... twice a week I dust with Reptivite...  I don't see the need for extra heat... they are digesting just fine apparently from all the droppings I see... they are well formed droppings and I don't think they would be any better with heat... but then again it's already 80° in the room.. in nature they hide in underground burrows during the day... I assume cause it's cooler down there... then when the temperature drops and the sun goes down they come up to feed.  Like I said if I saw they were not doing well I'd make the necessary adjusments but they seem fine the way they are.

As for using the lights as your heating... if you look online for leopard gecko set ups... half the world has lights on their set up and half the world might use mats... you gotta realize there are no absolutes in keeping some animals... while others are more particular.  As far as the light bothering them, I think that's why they have eyelids hahaha... just keep an eye on him... if he's eating and pooping and that really is a current tail picture then I say let him be... but that's my opinion only... 

I gave everyone who helped points for this question. I wish they would let me give infinite points so i could give u all 250 :)