Do male Dynastes Grantii beetles fight in a tank without females?

Dwarf gouramis can be very territorial. If your tank is not big enough, one will chase the other. Removing one fish or transfer to a larger tank may be necessary. You can determine sex by looking at the dorsal fin. The male's dorsal fin is pointed, while the female's is rounded or curved.

Unfortunately, it is common for intact males of the same species to fight, so you may experience that as they get older. They can be very territorial, and it doesn't matter if they are siblings or not. As you mentioned, male and female geckos can (and often will) mate, no matter if they are siblings or not. If you have two females, this would be the most ideal housing situation for multiple animals. Females will often tolerate one another in the same area, however there are exceptions to the rule, and they can fight as well.

Juveniles smaller than about 4 inches are difficult to sex. Once they reach that size or larger, it is quite simple.Female sliders are larger, have shorter front claws and thinner. smaller tails than males. Males can be territorial and could "argue" if the tank is not of sufficient size. Ideally, you want to allow about 10 gallons per inch of turtle. Sliders can get big (12 inches fully grown), so be sure you have the space and budget for a large tank.

Males are difficult because they can be territorial. This can result in aggression and potential injuries. Mixing different species is never recommended. Introducing a female may be your only option, but you risk breeding and unwanted or accidental clutches of eggs.

GloFish are schooling fish. They do best in groups of 6 or more. If you have just a few, they may be stressed which can cause aggression. Check the water parameters since an imbalance in chemistry can cause stress as well. You can use a home test kit (one with liquid drops, not test strips) or submit a sample to you local pet store or aquarist. Most will perform water testing for free or for a nominal fee. Ideal parameters measure 0 ppm (parts per million) ammonia and nitrites with nitrates at 40ppm or less. pH of the water should be between 6 and 8. They are cool water fish, so aim for a water temp between 65 F and 75 F. Hopefully, this will help. The other option you have is to remove the aggressor. You can request a consultation to discuss the situation and set up in greater detail or if you have further questions or concerns.

Usually siblings raised together will be able to live together. It sounds as if you have one overly dominant female though. You can try keeping them in a larger cage with additional bowls, bottles, toys and hides. This may give them enough "elbow room" which may decrease the squabbling. If not, you may need to separate them for a few days. A gradual reintroduction can be tried, but if they continue to fight, permanent separation may be the only option.

Aggression among Dobies of the same sex is well-documented and believed to be a breed specific trait with a genetic component. However, there has not been any research that has proven any one theory over another beyond a reasonable doubt. The reason they do not fight with the opposite sex is simple survival of the fittest. Obviously the breed could not continue to live on if the males and females were not able to coexist with one another. Hope this helps.