Axolotl with small gills

Two friends and I bought some axolotls about a year ago. Both of my friends axolotls have grown very large and have longs feathery gills. My axolotls seem to be pretty small and their gills are short and kind of shrunken. They are about 5 inches. Is this normal or is somethigng worng? I have them in a 30 gallon aquarium with a 4 inch sponge filter.

They look like they are on the skinny side and 5 inches is pretty short for 1 year old. So, let me ask questions about your tank set up, since that would affect growth rate.

What are you feeding them? How much? How often?

What temperature is the water at?

Do you have a test kit and are you testing for ammonia, nitrite, and nitrate regularly?

water temp is about 65 f. they are eating frozen blood worms and earthworms. I feed the blood worms every day and the earth worms about every other day. The blood worms come in individual "cups" about the size of a gumdrop and I give each axolotl 1. I do not have a test kit but I did just order one on amazon yesterday and its supposed to get here Wednesday.

OK, my semi-educated guess (I do not consider myself an expert) is that there is some off with the water parameters or they aren't getting enough food. Blood worms are also not considered a good diet (not nutritionally complete) once the axolotls are past a certain size. (I can't remember the size off hand, but I know it is less than 5 inches). I do not know if a bloodworm/earthworm mixed diet would cause slow growth, though. (I suspect not.)

Do you let them eat until stuffed? Given their small size, perhaps feeding a few times a day, as much as you can coax them to eat, would help them put on weight. You don't have to worry about over eating until they are full adult size. (You do have to make sure not to leave leftover food in the tank, however.)

How often are you changing the water and how much each time?

I do not know if there are any parasites that could cause slow growth - perhaps someone with more experience can speak to that.

I believe that the start in life often affects future growth....size and gills....and poor nutrition in those first months often cannot be undone.I have a 5year old who came to me third hand from a pub who is only half the size of those I have raised from eggs myself. His gills are poor...yet they live and eat together...so it can only have been his poor start.
At my daughters nursery they have his 3 siblings.....all equally small and short gilled...BUT SCOFF EARTHWORMS and are otherwise healthy.

I normally feed them until they wont eat any more. I will try to feed them a few times a day and see if that helps. I change about 25% of the water every week.
When I first got them they were babies and tiny. I fed them as much as they would eat so im not sure why they stayed small.

Can you get a picture from above? That is usually the easiest way to see if they are under/over weight. It could be the camera angle that is making the look skinny.

Also, did you get the axolotls from the same batch (litter, whatever you call a bunch of egg siblings) as your friends? Maybe there is some genetics involved. (But still, 5 inches seems rather small.)

Maybe the test kit will show something.

Good luck!

I tried to get a picture from above but I couldn't get a clear shot because of the glare from the water. My two friends got their axolotls from the same litter and they are big and have very large gills. mine is from a different litter. Maybe it could be genetic. Ill let you know the results of the test as soon as I get them

I'm definitely no expert but I would also suspect something is wrong with their water or diet, just given how skinny they look for their size. Have you ever noticed if they keep their food down or spit it back up? As others have said, I also recommend you do some research into what a more balanced diet is for axolotls. However, I also wonder if it could be genetics. Now, I'd still check into everything else, because you want to give them the best care possible, but there's always a chance of weird genetics too. Again, check everything with their water and diet but...

I figured I'd mention the genetics thing because I know someone who has an axolotl that is only about two or three inches long, despite perfect tank parameters and diet/care etc, it just grew into the smallest juvenile stage and has stayed that size for about a year now. It seems to just be a weird case, like a runt. (I'm not sure if that's the technically correct term for an amphibian but...)

Switch to live earthworms as a staple and throw in a few axies pellets a couple of times a week.
A 'healthy' weight for an axie is their stomach is approx as wide as their head. If your axies tummies are thinner then feed more/more often, if their tummies are bigger, cut back on the amount your feeding.
Bloodworms are not nutritionally enough for them once they are 4"+ so i would cut these out and only feed occasionally as a 'treat'.

Their gill size could be gentic but also gills tend to be smaller when your water is more oxygenated as they dont need as many fillaments to get the oxygen.

I also suspect your water parameters for Ammonia, NitrIte and nitrAte may be off, have you ever cycled your tank? This is important in keeping healthy aquatic animals. A sponge filter only does biological filtration it doesnt offer chemical filtration. Also a 4" sponge filter sounds pretty small for a 30 gallon tank, you may need to buy either another sponge filter or a filter that also chemically filters your tanks, i know a few members use the fluval filters.