Aquarium keeping is an art, a delicate balance of water chemistry, light, and choosing the right tank mates. But sometimes, certain fish just aren’t meant to be roomies.
In this list, we’ll explore aquatic combinations that tend to clash, why they don’t gel, and offer friendlier alternatives.
1. Cichlids and Tetras

Ever notice how big personalities clash? Cichlids, with their bold colors and assertive demeanor, often see smaller, peaceful tetras as mere background music.
This mismatch in temperament can lead to stress for the tetras. Opt for tank mates that match the cichlid’s vigor, like other robust cichlids or larger, calm fish that won’t be easily bullied.
2. Angelfish And Guppies

Angelfish have a certain grace about them, slow-moving and serene, while guppies are like the aquarium’s jitterbugs. Their energetic antics may irritate the angelfish, leading to nipping.
Instead, pair angelfish with calmer species like gouramis or larger tetras, who will match their tranquil pace and cohabit peacefully.
3. Oscars And Small Fish

Oscars are like the big, brash stars of the aquarium world, demanding attention. Place them with small fish, and they might become accidental snacks.
Not ideal, right? Instead, consider pairing Oscars with larger, equally bold fish like other sizable cichlids or robust catfish, ensuring harmony in the tank space.
4. Clownfish and Seahorses

Clownfish, the jesters of the sea, can be a little too playful for the gentle, slow-moving seahorse. This energy mismatch can lead to stress for the seahorse.
A better pairing for seahorses would be pipefish or other peaceful, slow-moving marine life that won’t disturb their serene existence.
5. Tiger Barbs And Angelfish

Imagine a party of tiger barbs, full of energy and mischief, flitting around a serene angelfish. It’s the classic tale of the prankster and the poet. Their nipping tendencies can annoy and stress angelfish.
Instead of that, tiger barbs thrive with similarly active fish like danios or larger barbs that enjoy their energetic play without the stress.
6. Discus and Gouramis

Discus fish are the sensitive artists of the aquarium, and they need a calm environment to thrive. Gouramis, though typically peaceful, can be too curious for discus’ liking. This can disturb the discus’s peace.
It’s better to house discus with other gentle species like tetras or peaceful bottom dwellers that won’t disrupt their tranquil habitat.
7. Arowanas And Small Fish

Arowanas are majestic creatures, commanding presence with their elongated bodies and graceful movements. However, small fish may find themselves on the menu next to an arowana.
To avoid a snack attack, pair arowanas with large, robust fish like stingrays or other big tank mates that can match their grandeur without becoming a meal.
8. Pufferfish and Slow Swimmers

Pufferfish have a penchant for being the center of attention, often investigating everything around them. Slow swimmers like gobies or blennies might get overwhelmed by their bold nature.
These interactions can lead to stress for slower fish. Instead, pair pufferfish with active, playful tank mates that enjoy their antics and pace.
9. Goldfish And Betta Fish

Picture this: a lavish goldfish flaunting its shimmering scales, swimming right into the personal bubble of the regal betta. It’s like putting a social butterfly next to a moody artist.
Both are gorgeous in their own right but keep them separate as they may turn territorial. Instead, pair your betta with relaxed tank mates like tetras or small catfish.
They’ll appreciate each other’s company without the drama.
10. Guppies And Betta Fish

A betta’s long, flowing fins are like waving a flag to playful guppies, who may mistake them for toys. This can lead to fin nipping, leaving the betta stressed.
Instead, bettas thrive with calm, non-nipping tank mates such as snails or peaceful bottom dwellers that respect their space and magnificence.
11. Bettas and Gouramis

Bettas are the divas of the fish world, wanting all the spotlight, while gouramis can be equally attention-seeking. This clash of egos often leads to territorial disputes.
Bettas prefer quieter company like peaceful shrimp or smaller fish that won’t compete for space or attention, maintaining a tranquil tank environment.
12. Neon Tetras And Goldfish

Neon tetras are tiny, delicate creatures, and goldfish are like the gentle giants who might not know their own strength. The temperature preferences also clash, making it uncomfortable for both.
Instead, neon tetras swim happily with other small, tropical species like rasboras or small catfish that share similar needs and environments.
13. Plecos and Discus Fish

Plecos are the janitors of the aquarium, diligently cleaning surfaces, but their nocturnal habits can disturb the peace of discus fish. Discus prefer calm, stable environments without nocturnal commotion. Instead, pair discus with small, peaceful fish that don’t disrupt their space, ensuring a restful habitat for these sensitive souls.
14. Molly Fish And Tiger Barbs

Molly fish are peaceful grazers, while tiger barbs are the hyperactive troublemakers of the aquarium. This mismatch can lead to unwanted stress and fin nipping for mollies.
Consider housing mollies with other peaceful species like platies or guppies that share their easygoing vibe and reduce tension in the tank.
15. Bettas And Fancy Guppies

The elaborate fins of fancy guppies can incite jealousy and aggression in bettas, who see them as rivals for beauty and space. This can lead to chasing and fin damage.
To keep peace, opt for tank mates for bettas that are less flashy, such as peaceful shrimp or small schooling fish that won’t threaten their vanity or territory.