dragon poo should be a formed brown mass, not super hard or really soft. It should hold its shape and look like a cigar shape. Often with poo is a section of white, off-white or even tan colored hard chalky piece. This is the urates.
Depending on the diet of the dragon and if there were recent changes, there are lots of variety in dragon poop consistency. If fed heavily on superworms, crickets and other 'hard bodied' insects, then the poop tends to be more chunky..as undigested exoskeletons are passed (hence why it is recommended not to feed excessive amounts of hard bodied insects, especially with baby dragons). Feeding soft bodied insects (ie silkworms, butterworms, hornworms etc) can lead to much softer stools, though they should still be relatively formed. This is normal, as the higher water content and very soft and easily digestible exoskeletons of caterpillar type worms, just means less hard waste material.
Sudden changes to diet or feeding too much high water greens, can lead to very soft and runny stools. This is ok other than the fact most high water greens (ie iceberg lettice especially) are very poor nutrition wise and shouldn't be fed at all.
The only time soft stools are an issue is if they are constant (especially if no diet changes have happened in the last several weeks) and smell much more fouler than normal. This often indicates internal parasites. A fresh sample should be taken to a vet to be examined for signs of parasites. Once parasites are detected, vets will need to see your dragon to properly set dosage. (pretty much to weigh the dragon and see if its healthy enough to tolerate medical treatment, or to examine him for other reasons).
Note: If you feed any colored pellets to your dragon, expect the poop will come out odd colors. This is ok, as the dyes used in the pellets are not used by the body and are flushed out in the only way the body can.
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PHLdyPayne