Impaction is a condidtion that is shown in reptiles it is a very common problem in geckos and beared dragons.
This is when a foreign object that it can not diggest becomes blocked within the difestive tract. this can turn out to be fatal
 

If you believe your reptile to be impacted then stop feeding and seek a vets advice - feeding will only help block the intestines and worsen the situation. Impaction can usually be seen through a lack of eating, a swollen or distended black/ blue abdomen.

 

Causes

Impaction is caused by swallowing objects that the animal can not digest such as substrate's that are loose, Plastic plants with loose leafs that are able to fall off and unsuitable food items.

Impaction is mainly found to be sand, small rocks and parts of decor.

 

Symptons

Abnormally large, dark spots on belly (do not mistake for other organs)

Twitching, low usage of, or total paralysis of back legs

Little to no appetite

Lethargy

Difficulty passing stool

Abnormally small, hard, dry poos

Poos with nothing but substrate in them

No poo at all.

 

Prevention

The first line of defence against impaction is prevention. DO NOT use loose substrate (sand/calci sand/playsand, aspen, wood chippings etc)
Unfortunatley for beginners if you go out to buy a "full set up" which is not the case as it usually misses items anyways - every set up ive looked at contains a 5kg bag of sand (Based on the shops in my surrounding area). Ask the shop to exchange the sand for another item of substrate like repti carpet as you dont want to use sand most shops are more then happy to swap the sand if they arnt willing to then just DO NOT use the sand find another use with it or simply get rid of it.

 

Decor can raise a few issues, if they are old plants or weak non-durable plants its better to replace or move out of a way that it could become a harm to the gecko (So anything like leaf's falling off to stones dropping from the plants stands etc). Young geckos at birth to around a year may benifit more from a basic set up rather then a full set up with lots of deco. you could add plants as they get older and a bit more sensible with food.

 

Food being another reason of impaction is largely due to "hard" food or food that is to large. A lot of insects form a harder casing/outer shell.

• Mini mealworms - are best to feed to babies as they not fully developed like a mealworm and therefore have a softer shell

• Brown crickets have soft bodies compared to a black cricket which has a hard shell back.

• Locusts grow slowly and have soft bodies. (also better nutrtion wise compared to crickets)

• Dubia roaches tend to have a soft shell compared to other roaches available for other reptiles.

 

Feeding to large of a insect can prove to cause issues, but is rarely seen only feed geckos a adequate sized insect. For babies and juvieniles food items should be lo larger then the gap between the eyes. Adults you can feed bigger insects but not to big that they struggle to eat. 
Unfortunately a lot of stores either go Grade1,2,3,4,5,6 insects or you get Size s,m,l,xl so there isnt a balanced answer that we can say to use. Normally (once again based on my stores) grade 4 and 5 or L is fine for adults - Juveniles grade 2 and S are normally alright sometimes medium depends on the store i go to.