Best Guppy Tank Mates: Compatible Species

Why guppies are easy community fish (and where they still go wrong)

Guppies earn their reputation as the ideal starter fish for good reasons. They're small - males top out around 3-4 cm (1.2-1.5 in), females around 5-6 cm (2-2.4 in) - peaceful, and unfussy about water chemistry compared to many tropical species. Farm-raised strains sold in most shops will adapt to anything from soft, slightly acidic water to hard, alkaline tap water, as long as your cycle is established and parameters stay stable.

The problem most new keepers run into isn't finding compatible tank mates. It's underestimating how fast guppies breed. A trio of females can produce 20-50 fry every four to six weeks. Within three months, a 60 L tank that started with six guppies can be sheltering forty. That biomass hits your nitrogen cycle hard, and any tank mates you added are now crowded out. Plan your stocking around the breeding output, not just the fish you buy on day one. If you haven't cycled your tank yet, read how to cycle a fish tank before adding anything.

Compatible species: what actually works

Platies (Xiphophorus maculatus)

Platies share almost identical water requirements with guppies - pH 7.0-8.2, temperature 22-26 °C (72-79 °F) - and have a similar calm temperament. They're slightly stockier and slower than guppies, which means they compete fairly at feeding time without bullying. A mixed community of guppies and platies in an 80 L tank works well at around 6-8 fish total before breeding pressure builds.

One caveat: platies are also livebearers and breed prolifically. In a mixed tank you'll be managing two breeding populations simultaneously. That's manageable if you're deliberate about it, but it catches a lot of beginners off guard.

Mollies (Poecilia sphenops / P. latipinna)

Mollies overlap heavily with guppies on water parameters, though they genuinely prefer the harder, more alkaline end of the range - pH 7.5-8.5 and temperatures of 24-28 °C (75-82 °F). If your tap water is hard, mollies are a natural fit alongside guppies. If you're in a soft-water area, guppies will cope better than mollies will.

Short-finned mollies are the safer choice over sailfin varieties in a guppy community. Sailfins grow to 12 cm (4.7 in) and can become mildly territorial in smaller tanks, particularly the males.

Harlequin rasboras (Trigonostigma heteromorpha)

This is one of the most underrated guppy companions. Harlequin rasboras are shoaling fish that occupy the mid-water column, rarely compete with guppies for territory, and don't breed in standard freshwater tanks (they need specific soft, acidic conditions to spawn). That last point matters - they won't add to your population pressure. Keep them in groups of six or more; a lone harlequin is a stressed harlequin. They prefer slightly softer, more acidic water than guppies ideally want (pH 6.0-7.5), but both species adapt well to the neutral 7.0-7.5 zone that most tap water sits in.

Corydoras catfish (Corydoras spp.)

Corydoras are bottom dwellers that clean up uneaten food before it rots - genuinely useful in a guppy tank where surface feeding means a lot of food sinks. Corydoras sterbai and C. panda are both good choices; they tolerate temperatures up to 28 °C (82 °F) better than the cold-preferring C. paleatus (which is more comfortable at 18-22 °C / 64-72 °F and often listed as a guppy companion despite the temperature mismatch). Keep Corydoras in groups of at least four - they're social and become inactive and stressed in smaller numbers.

Otocinclus (Otocinclus spp.)

Otocinclus are small algae-grazing catfish that top out at about 4 cm (1.6 in). They're peaceful, occupy a completely different niche to guppies, and are genuinely effective at keeping glass and plant leaves clean. They do have two real weaknesses: they're fragile when first imported (buy from a shop that's had them in stock for at least a week), and they need an established tank with genuine algae growth to graze - a brand new, algae-free setup will starve them. Supplement with blanched courgette or algae wafers once or twice a week regardless.

Swordtails (Xiphophorus hellerii)

Swordtails work in larger tanks - 100 L (26 gal) and up. Males can be mildly aggressive toward each other and occasionally harass smaller fish in confined spaces. The bigger concern is size: males reach 10-14 cm (4-5.5 in) including the sword extension, and in a small tank they can stress guppies simply by dominating space. Stick to one male swordtail in a mixed community, and give the tank enough footprint that everyone can spread out.

Fish to avoid with guppies

Bettas (Betta splendens)

This combination fails more often than it succeeds, despite being widely suggested. The problem runs both ways. Male guppies have large, flowing fins and bright colours - exactly the visual triggers that provoke a male betta. The betta will often shred guppy fins within hours. Less commonly discussed: a group of guppies can mob and nip a betta's fins in return, particularly in a small tank. There are individual bettas that coexist with guppies peacefully, but you're gambling on temperament, and there's no way to predict it before the fish are in the same water.

Tiger barbs (Puntigrus tetrazona)

Tiger barbs are notorious fin nippers, and guppies' long tails are a direct provocation. Even keeping tiger barbs in large groups (eight or more, which does reduce nipping between themselves) doesn't reliably protect long-finned tank mates. Keep them in a species-appropriate setup, not a guppy community.

Large angelfish (Pterophyllum scalare)

Adult angelfish will eat adult guppies. That's not aggression - it's predation. Angelfish reach 15 cm (6 in) in body height and are ambush predators of small fish in the wild. Juvenile angelfish may coexist briefly, but once they grow, the guppies disappear. Don't combine them.

Other fish to skip

Avoid cichlids as a general rule - even "peaceful" cichlids like rams can be unpredictable with fish as small as guppies during spawning. Goldfish are a non-starter: they need cooler water (15-20 °C / 59-68 °F), produce massive waste loads, and will eat guppy fry. Red-tailed sharks and rainbow sharks are territorial bottom fish that will stress any small, mid-swimming fish sharing their space.

Setting up a guppy community tank that stays stable

Tank size and footprint

The 40 L (10 gal) minimum gets you started with guppies alone. For a real multi-species community - guppies, a Corydoras group, and a small rasbora shoal - 80 L (20 gal) is a more honest starting point, and 120 L (30 gal) gives you meaningful flexibility. Long tanks are better than tall ones for guppies and Corydoras, both of which appreciate horizontal swimming space over depth.

Managing the breeding problem

The single most effective strategy is keeping only males. A male-only guppy tank is colourful, active, and won't crash your stocking numbers. Males will occasionally chase each other, but in a group of six or more in a well-planted tank, this rarely causes real harm.

If you want a mixed-sex group, a 1:2 or 1:3 male-to-female ratio reduces harassment of individual females. But plan from day one what you'll do with fry - local fish shops, aquarium clubs, and online hobbyist groups will often take healthy fry, but you need to move them before they add to your tank's bioload. Track your water test results and stocking changes in App-aquatic - it's useful for spotting when ammonia starts creeping up as your population grows.

Water parameters and stability

Target pH 7.2-7.8 and temperature 24-26 °C (75-79 °F) and you'll be in the comfort zone for guppies, platies, mollies, and most community Corydoras simultaneously. Stability matters more than hitting an exact number - a tank that holds pH 7.4 consistently is better than one that swings between 7.0 and 8.0. Read more about what to test and why in our guide to aquarium water parameters.

Feeding a mixed community

Guppies feed at the surface and mid-water. Corydoras and Otocinclus feed from the bottom. Feed your surface fish first to draw them up, then drop sinking wafers or pellets to the bottom while the guppies are occupied. If everything hits the surface at once, your bottom feeders don't eat. Twice-daily small feedings work better than one large feeding for water quality - less uneaten food reaches the substrate. See how often to do water changes for guidance on keeping up with the waste load a community produces.

What most guppy guides miss

Most compatibility lists focus purely on aggression. They ignore density. A "compatible" species that doubles your tank's bioload creates water quality problems that kill fish just as effectively as a bully does - it just takes longer and is harder to diagnose. Before you add any species, run the numbers on your actual tank volume against your planned stocking. The free stocking calculator accounts for tank size, filtration, and species-specific bioload in a way that the old "one inch per gallon" rule simply doesn't.

The other thing that goes unmentioned: guppy strains matter. Wild-type and feeder guppies are genuinely hardier than heavily selectively-bred fancy varieties. Long-finned, double-sworded, or Moscow Blue strains have been bred for appearance at some cost to vigour and fin integrity. Fancy males in a community with even mildly active fish will have their fins nipped more frequently and recover more slowly. If you want to keep fancy guppies, a species-only tank is often the more practical setup.