Eastern mudminnow

Where they come from

Eastern mudminnows are little swamp and ditch specialists from the coastal plain of the eastern US. You find them in weedy backwaters, cranberry bog-style ponds, slow creeks, and mucky marsh edges where the water can get warm, tea-colored, and low in oxygen.

That background explains basically everything about them in a tank: they like cover, they do fine in still or gentle flow, and they are tougher than they look as long as you keep the water clean and the feeding steady.

Setting up their tank

Give them space to poke around and a lot of structure. I have had the best luck starting at 20 gallons for a small group, mostly because you can build a nice maze of plants and wood without it feeling cramped.

• Tank size: 20 long is a great starting point for 3-5 fish; bigger is easier if you want tankmates
• Filtration: sponge filter or a HOB with the flow turned down; they do not need a river
• Substrate: sand or fine gravel; leaf litter on top if you like a natural look
• Hardscape: driftwood, root tangles, piles of branches, rock caves (smooth edges)
• Plants: anything that makes thickets - hornwort, anacharis, water sprite, java fern, floaters

They are escape artists in that annoying, surprising way. If there is a gap in the lid, they will eventually find it. A tight-fitting cover and plugging cable gaps saves you from the worst kind of floor discovery.

Water parameters are not a place to obsess with this species, but stability matters. Neutral-ish pH is fine, moderate hardness is fine, and they handle cooler water well. I keep mine in the upper 60s to low 70s F most of the year, and they act more relaxed and live longer than when kept warm all the time.

What to feed them

Think small predator with a big mouth for its size. Mine went crazy for live and frozen foods and were only so-so on dry food at first. Once they recognize pellets as food, they will take them, but you usually have to win them over.

• Staples: frozen bloodworms, blackworms, chopped earthworms, brine shrimp, mysis
• Live treats: daphnia, mosquito larvae (if you trust the source), small worms
• Dry options: sinking carnivore pellets, micro pellets, crushed high-protein sticks
• Avoid: feeder fish (parasites) and making them live on only flakes (they get skinny)

Feed smaller portions more often if you can. They have that 'hang out and ambush' vibe, so they may look like they are not hungry and then suddenly inhale three worms. Watch body shape: you want them solid, not pinched behind the head, and not football-round.

How they behave and who they get along with

Mudminnows are curious and a little sneaky. They spend a lot of time hovering in plants, then scoot out to investigate anything new. They are not nonstop swimmers like danios, more like a mini pike that decided to live in the weeds.

They will eat anything that fits in their mouth, and their mouth fits more than you think. That is the main rule for tankmates. They are usually not aggressive in the 'chase and shred' sense, but predation is predation.

• Good tankmates: larger minnows/shiners that stay too big to swallow, peaceful sunfish-sized companions in big tanks, hardy coolwater species
• Use caution: slow fancy fish (they will nip sometimes), small catfish that might get outcompeted at feeding
• Not a match: tiny tetras/rasboras, small shrimp, guppy fry, anything bite-sized

I like them either solo with a really interesting scape, or in a group with heavy cover. Groups can work well as long as everyone gets food. Drop food in two different areas so the bossy one cannot park on the buffet.

Breeding tips

They can be bred in aquariums, and it is a fun project if you enjoy observing behavior. The big trigger tends to be seasonal rhythm: cooler period, then a warm-up with heavier feeding and lots of plant cover.

• Give them a winter: several weeks on the cool side with shorter light, then slowly warm and lengthen the photoperiod
• Feed hard before the warm-up: worms and frozen foods build condition fast
• Spawning media: dense plants, spawning mops, or leaf litter where eggs can stick and hide
• Remove adults or move eggs: they will snack if they find them

If you get fry, start small: infusoria-rich plant clumps help a lot, then move to baby brine shrimp and finely crushed foods. Keep the tank very clean but do not blast them with current.

Common problems to watch for

Most issues I have seen with mudminnows come from three things: too warm for too long, not enough cover, or food that does not match what they want. Fix those and they are usually very forgiving fish.

• Jumping: nearly always a lid or gap problem
• Skinny fish: getting outcompeted in groups, or offered only flakes/pellets they are not actually eating
• Sulking and hiding all day: too bright, not enough plants/wood, or tankmates that are too active
• Bloat/constipation: overdoing dry foods; add more frozen/live and keep portions reasonable
• Ich after new additions: quarantine helps; they handle standard treatments, but go gentle with heat-based approaches

If you are buying or collecting them (where legal), look for clear eyes, intact fins, and a fish that reacts to movement instead of just sitting on the bottom breathing hard. A healthy mudminnow is alert and does that quick, confident dart into cover.