If the lump is covered with scales, and the scales are a continuation of their normal scales / skin(?) then it is probably a tumor. It is easiest to check this by using a torch to directly shine light on the lump, but please don't shine it in their eyes! If it is not covered with scales, then it is likely to be an external parasite.
It is quite possible for Bettas to live a long-ish and happy life with a tumor, but sometimes the tumor affects more of their body than you can see, and they pass away.
Tumors are very common with Bettas, due to inbreeding and hormone therapy when they are young to make them grow quicker, to make more money.
Normally the male betta fish has much longer flowing fins than the female.
The female betta fish has vagina lips on its anus.
betta fish are unpredictable so you couldn't really tell
It's all in the tail. the males is larger and longer and the females is shorter.
Yes a betta fish can become overweight if they are fed to much. You can tell a betta is overweight when their bellies are round and protrude away from their bodies.
The male Betta fights with other male Betta and the female don't
Unfortunately, there is no easy way to tell the age of a fish.
I'm terribly sorry to tell you this, but it might be a tumor. :( bettas live 1-2 years, so it might be getting older which causes it to get a tumor. it may not be a tumor, and not all tumors are cancer. good luck all the best, Fishlover
A betta fish tatto would be a tattoo of a betta fish.
Betta fish sleep on the bottom of the tank. I've never seen one close its eyes but they will often rest on the bottom when there is no action going on around them. Betta like to be around movement. That is why we have my betta fish in our living room.
Female betta fish lay eggs. If the female has vertical stripes that stand out, she is going to lay her eggs soon.