The marigold variatus is a color variety of the variatus platy (Xiphophorus variatus). Generally, these fish are not particularly aggressive. However, they do have a few personality quirks you need to take into consideration when selecting tank mates.
Platys are considered community aquarium fish. That means these fish rarely bother other fish and they get along with most other peaceful aquarium fish. For the most part, you need to worry more about other fish picking on your platys rather than the platys bothering them. Their easygoing nature makes them ideal fish for beginners.
Variatus platy are closely related to another common aquarium fish, the swordtail. These fish are so closely related that they hybridize readily. Most pet shop platys have some swordtail ancestry as a result of crosses designed to create new color varieties. Since swordtails are more aggressive, this can produce fish that are somewhat more feisty than usual. However, this aggression is still quite mild, at the most taking the form of fin-nipping.
The biggest concern with platys' aggression is fin-nipping. For this reason, avoid fish with long, flowing fins like bettas and freshwater angelfish. Also, because of their readiness to hybridize, you should not keep them with fish from the same genus, including swordtails (X. hellerii) and spotted platys (X. maculatus).
Oddly, marigold variatus platys are at their most aggressive with members of their own species. Within their school, they form a hierarchy, with a male at top. Unlike their swordtail relatives, the hierarchy is mild, and fish at the bottom usually still get enough to eat and don't suffer for their low rank. Also, males tend to constantly mate with females, so you should stack your school with a ratio of one male per two females -- at least.
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