Chestnut lamprey

Where they come from

Chestnut lampreys are a native North American river fish, not the invasive sea lamprey everyone hears about. You find them across the Mississippi River basin and connected drainages, where cool, clear streams roll into bigger rivers. Adults cruise deeper runs and lakes to feed, then head back to gravelly riffles in spring to spawn.

Setting up their tank

I kept an adult in a 75-gallon coldwater river setup. The two things that matter most are cold, oxygen-rich water and a steady current. If you can nail those, you are halfway there.

• Tank size: 55-75 gallons for one adult. Go bigger if you add a sand refugium for larvae.
• Temperature: 48-64 F (9-18 C) most of the year. Try not to let it sit above 68 F (20 C). A chiller makes life easier.
• Flow: Strong, laminar current. Aim for 6-10x turnover with a canister filter plus a powerhead. Lots of surface agitation.
• Substrate: Rounded river stones and gravel with open patches. Adults wedge under rocks; they do not burrow like larvae.
• For larvae (if you keep them): a separate tray or refugium with 2-4 inches of fine sand-mud mix and gentle through-flow.
• Decor: Smooth cobbles, slate stacks, and driftwood. No sharp edges around the intake. They rasp with a soft mouth.
• Filtration: Oversized canister with prefilter sponges. Meaty feeds foul water fast, so overbuild the biofilter.
• Lid: Tight-fitting with blocks around cables. Lampreys are escape artists and will follow trickles right out.
• Lighting: Dim. They are more active at dusk or with blue moonlights.

Cycle the tank fully and keep it mature. I did 25-40% weekly water changes, more after heavy feeds. Keep pH stable in the 6.8-8.0 range and avoid sudden swings.

What to feed them

Adults are parasitic in the wild, which is why this species is a challenge in aquaria. You do not need to give them live hosts. Mine took hand-fed strips of fish and shellfish. The trick is letting them latch on and rasp without the food skittering away.

• Good staples: tilapia or salmon fillet, smelt, shrimp, squid rings, nightcrawlers. Rinse well and use small, firm strips.
• Presentation: hold with tongs near the mouth; once the disc latches, keep it steady for several minutes.
• Schedule: 2-3 times per week for adults. Offer until they stop rasping strongly.
• Supplements: a tiny smear of vitamin-fish oil on fillet once a week helped condition mine.
• For larvae: they filter-feed. Use green water, spirulina powder slurries, or a tiny pinch of baker's yeast in a separate sand tray with gentle flow. Go very light to avoid fouling.

How they behave and who they get along with

They are calm but purposeful. Mine spent days tucked under a rock in the current, then went exploring after lights down. They climb glass and cords with shocking skill, so that lid really matters.

• Tankmates: best kept alone. Any fish is a potential host.
• Inverts: tough snails and freshwater mussels usually get ignored, but strong flow can be rough on them.
• Handling: use wet hands or a soft container. Nets snag their skin and gill openings.
• Activity: more active in cool water and dusk lighting. Warmer temps make them restless and stressy.

Breeding tips

They have a long, staged life cycle. Larvae (ammocoetes) live burrowed in fine sediment for several years filtering tiny particles. After metamorphosis, they become parasitic adults for a year or two, then spawn in spring on clean gravel riffles and die. Pulling that off indoors is way beyond normal fishroom work.

• To even try, you'd need seasonal cooling and warming, a strong current over clean gravel, and a group to build a nest.
• Adults do not eat while spawning and die afterward.
• Raising larvae requires a dedicated sand bed with gentle flow and very light, frequent microfeeds. Water quality is the hurdle.

Common problems to watch for

• Overheating: anything above 68-70 F for long stretches is rough on them.
• Low oxygen: they wilt fast without strong flow. Keep intakes clean and powerheads serviced.
• Escapes: gaps around cables or canister returns are classic exit routes.
• Starvation after metamorphosis: newly transformed lampreys may refuse food at first. Offer small, fresh strips daily and keep the room quiet.
• Mouth abrasions and fungus: rough rocks or dirty food can cause issues around the oral disc. Swap to smoother decor and pristine food handling.
• Water quality swings: meaty feeds spike ammonia. Use prefilters, big water changes, and test often.
• Legal and ethical headaches: some regions restrict transport or release. Never move them between watersheds.