Personally, I wouldn't, but I've had bad experiences.
And while others have enough experience to judge whether disease or some non-contagious cause is involved, I lack this myself.
I bought some Glowlight Tetras some time back which had deformities not noticeable in the sales tank, being unable to recognise the signs of a mycobacterial infection I didn't then realize was generally prevalent among aquarium fish or a problem to watch for.
Not sure right now whether I had those particular fish one or two years, but the three survivors, (1 being obese and 2 being small, skinny, oddly shaped and failing to grow as well as being bent,) lasted until weakened by a worsening bullying problem, and the added stress involved in the removal of the bullies (fast and sneaky Gold tetras) weakened not only them but one of the Black Neons purchased later (don't know if he arrived with a problem or acquired it, as the others were OK, apart from the one dying of injuries inflicted by the bully) who had failed to grow and exhibited symptoms including progressive 'tail-dragging' - to the point where they could barely drag their tails up off the ground at all, and they were put down with clove oil before the shrimp had any opportunity to eat them alive.
I could still absolutely weep over that, especially as my big, beautiful Neons are also decidedly unwell, although getting around OK, and the wide-range antibiotic I tried in the tank, in the hope that in this case it was some other, treatable infection, killed my Amano-type algae shrimp, Nerite snail, and a number of hardy pond-type snails, although labelled as well-tolerated by invertebrates.
So - boom - down to 6 tetras and a small feeder-type guppy in my 35 gal. although my pygmy cats and the tip of my dwarf plec's tail still seem to be OK, knock wood.
I tend to get pretty attached to my fish, and I'm not good at losing them.
It's hard even to talk about it, but the warning should be given.
I know I will never knowingly buy any deformed fish again, unless I'm taking Betta culls or something.
The possible results can be devastating for all concerned.
I bought 6 White Clouds for one of my other tanks a while back, one with grossly severe spinal deformities, which was, however regretfully, put down, as I couldn't be sure she wasn't shedding organisms which could potentially affect other fish when stress of any type weakened their systems.
Healthy fish are resistant to disease - but, personally, I'd really rather not introduce avoidable potential problems into a tank with existing fish or one where others will be added.
And I wish I'd been aware of the nature and extent of these potential issues before I'd dismissed the problem as something non-contagious and exposed other fish.
There are a number of potential causes for deformity in fish - nearly all of them will bring, at best, fish susceptible to disease into your tank.
However, if the fish are being kept separately, the worst concerns don't apply, and you can provide a good home to fish most in need of one.
And if nothing ever goes wrong to lower any animal's immune system, many of these diseases are unlikely to spread.
I've just done a fast Google for what may not be the best examples, but give a general overview.
If anyone's interested, they're below.
http
/www.fishdeals.com/fish_diseases/curved_spine/
Obesity, unmentioned on this site, can be another symptom, due to liver damage/internal granulation.
http/en.allexperts.com/q/Freshwater-Aqua...ish-disease.htm
... It is possible for other fish to have a disease called Neon Tetra Disease. In advanced stages it can cause a curved spine. Early symptoms of this disease is loss of colour and erratic swimming behaviour. This disease is incurable and the fish usually dies a slow painful death. ...
'Whirling disease can also affect aquarium fish.
http/www.merckvetmanual.com/mvm/index.js...m/bc/170411.htm
... Myxosoma cerebralis , an important pathogen of young salmonids, is responsible for whirling disease, also known as “blacktail.” Typically, infected fingerlings show rapid tail-chasing behavior when startled, and the peduncle and tail may darken significantly. As infected fish age, skeletal deformity may result from damage to the cartilaginous structures, particularly the skull and vertebral column. Recovered fish remain carriers, and adults do not show signs, although skeletal deformities do not resolve. The disease can be prevented by purchasing uninfected breeding stock and maintaining them in an environment free of the intermediate hosts. A presumptive diagnosis of whirling disease is made by detection of spores from skulls of infected fish. Samples can be submitted to a fish disease laboratory, or procedures described by the American Fisheries Society can be followed. Diagnosis may be confirmed histologically or serologically. Whirling disease is of regulatory concern in some states. ...
http/www.aquariumpros.com/articles/nutrition.shtml
... Signs of nutritional deficiencies in fish range from physical deformities, a lowered resistance to disease, lateral line erosion, loss of scales, and listlessness to physical blindness. When these problems show up in an aquarium, there is a high probability that a poor diet is to blame. Please! Vary the diet of your fish. If you only feed flake food, your fish will develop horrible, irreversible malformations and they will only live a short while! ...
... Most fish also require at least six hours of the correct spectrum of light a day to manufacture certain vitamins and to process components of their diet. Aquarium light bulbs are special bulbs that simulate the spectrum of the sun. After a year of use, the bulbs no longer produce the correct spectrum and should be replaced. ...
Chemical pollution is present within drinking water as well, and is associated with deformities.
http/www.fws.gov/contaminants/Issues/Amphibians.cfm
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