Rainbow fish and killifish compatibility

I have some Angel fish with a killifish. They don’t bother each other but I put a new rainbow fish in and my killifish won’t stop following them around and flaring his fins out and occasionally gills. He hasn’t bitten the rainbow fish but he will stay within a few inches of it sometimes just being relaxed and other times following and flaring fins. Is this aggression that I should worry about? Or will they sort it out? Should I get another rainbow to change the power dynamics? Or will this be an incompatible species?

BBfishes said:

I have some Angel fish with a killifish. They don’t bother each other but I put a new rainbow fish in and my killifish won’t stop following them around and flaring his fins out and occasionally gills. He hasn’t bitten the rainbow fish but he will stay within a few inches of it sometimes just being relaxed and other times following and flaring fins. Is this aggression that I should worry about? Or will they sort it out? Should I get another rainbow to change the power dynamics? Or will this be an incompatible species?

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i think since they look similar he's trying either to set a pecking order or to breed
edit: pecking order happens in most new similar fish added to a tank (btw your killi is so pretty! its like a betta)

All rainbowfish need to be kept in groups of at least 6 (preferably 10) or more. Have males and females in the group. Try to keep males in even numbers and the same size (eg: 2, 4 or 6 males). You can mix different species of rainbowfish as long as they all grow to the same size. Fortunately most do.

You have a male gold panchax killifish that is showing off to a male Melanotaenia boesemani (rainbowfish). The panchax is a territorial display aimed at driving other males out of its territory. It doesn't normally do any harm and the rainbowfish will probably display back when it has settled into the tank.

The rainbowfish looks pale and has very pink gills, which could be an indication of poor water quality, gill flukes or something else.
Is the rainbowfish eating well and doing normal poop?

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What is the ammonia, nitrite & nitrate of the water?

What are the tank dimensions (length x width x height)?

What is the GH (general hardness), KH (carbonate hardness) and pH of your water supply?
This information can usually be obtained from your water supply company's website or by telephoning them. If they can't help you, take a glass full of tap water to the local pet shop and get them to test it for you. Write the results down (in numbers) when they do the tests. And ask them what the results are in (eg: ppm, dGH, or something else).

Depending on what the GH of your water is, will determine what fish you should keep.

Angelfish, most tetras, barbs, Bettas, gouramis, rasbora, Corydoras and small species of suckermouth catfish all occur in soft water (GH below 150ppm) and a pH below 7.0.

Livebearers (guppies, platies, swordtails, mollies), rainbowfish and goldfish occur in medium hard water with a GH around 200-250ppm and a pH above 7.0.

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Make sure the rainbowfish gets plenty of plant matter or plant based food in its diet. Their diet should be about half plant based and the rest can be insects, fish, prawn or anything else they will eat.

The following link has information and picures of all the known rainbowfishes from Australia and New guinea. You can go through them and see if any interest you.