Blotched eelpout

Where they come from

Blotched eelpouts (Zoarces gillii) are cold-water fish from the Pacific coast of North America. Think rocky shorelines, eelgrass, tidepools, and murky nearshore water where salinity swings with rain, runoff, and tides. That background explains a lot: they like it cool, they like hiding spots, and they do not appreciate tropical-style setups.

Setting up their tank

Plan your tank around three things: cold water, lots of cover, and escape-proofing. They are chunky, bendy, and stronger than they look, and they will test lids and gaps.

For a single adult, I would not bother with anything under a 40 breeder footprint, and bigger is calmer. They spend a lot of time parked under structure, but they still need room to cruise and turn without scraping themselves on rockwork.

• Temperature: cool and stable. Aim roughly 50-60F (10-16C). A chiller is usually not optional in most homes.
• Salinity: true brackish to light marine works. Pick a target specific gravity and keep it steady (around 1.005-1.015 is a reasonable brackish range).
• Filtration: oversized biofiltration plus strong mechanical. They are messy eaters and the food is meaty.
• Flow: moderate. Give them calmer pockets behind rocks and a bit of current in open areas.
• Substrate: sand or smooth small gravel. Skip sharp crushed coral if you are doing rock piles.
• Hardscape: rock caves, PVC sections hidden under rock, and tight crevices. They love a snug den.
• Lid: tight fitting with no cable gaps. Cover overflows and weirs if you have a sump.

Lighting can be pretty simple. Mine did best with dim to moderate light and a bunch of shaded areas. If you want plants, think brackish-tolerant stuff (or go with macroalgae if you are closer to marine), but honestly the fish does not care as long as it has cover.

What to feed them

They are carnivores and they eat like a little ambush predator. The trick is getting them onto reliable foods and not letting a shy eelpout starve while bolder tankmates hoover everything.

• Staples I have had the best luck with: thawed silversides, chopped shrimp, squid, clam, and chunks of marine fish flesh
• Good variety items: mysis, krill (not as the only food), chopped earthworms (works surprisingly well in brackish setups)
• Training foods: scented frozen blends, or soaking pieces in clam juice to get a feeding response

Target feeding with tongs makes life easier. I feed after lights are lower, put the food right at the mouth of their cave, and wait. Once they learn the routine, they come out fast.

How they behave and who they get along with

Blotched eelpouts are mostly chill, but they are still predators with a big mouth and a strong bite. They are also pretty fearless once settled in. Mine spent days hiding at first, then turned into a confident little log that would dart out and grab food like a snake.

Tankmates are where people get burned. Anything small enough to fit in the mouth is food. Anything that constantly nips or harasses them will stress them out, and stressed eelpouts go off food.

• Best kept: species-only, or with a few carefully chosen cold/brackish fish that are too big to be eaten
• Avoid: small gobies, juvenile mollies, ghost shrimp, and basically any "cleanup crew" you expect to survive
• Avoid: aggressive fin-nippers and fast, hyper feeders that steal every bite

Breeding tips

Breeding is possible but this is not a casual weekend project. Zoarces are livebearers (they give birth to well-developed young), and the seasonality and temperature cycling matter a lot more than most hobby fish.

If you want to try, start by keeping a small group in a big cold system so you can let a pair form naturally. Provide multiple tight dens and visual breaks, and feed heavy on varied marine meats for months. Many keepers also mimic a cooler winter period and a gradual warm-up into spring, but you have to do that without swinging salinity or letting water quality slide.

Common problems to watch for

• Running too warm: loss of appetite, restless behavior, faster decline over months
• Gaps in lids: overnight carpet surfing. They can wedge through surprisingly small openings
• Poor oxygenation: cold water holds oxygen well, but heavy feeding and low flow areas can still cause issues
• Water quality swings: big meaty foods mean nitrate and dissolved organics creep up if you slack on maintenance
• Injuries from sharp rock or tight squeezing: scraped skin, frayed fins, slow healing
• Parasites from live foods or wild collection: flashing, excess slime, refusing food

The best "preventative medicine" with this fish is boring stuff done consistently: keep it cold, keep it clean, and feed a variety without overdoing it. If something looks off, do not guess - test your water, check temperature, and watch the fish after dark with a dim light. A lot of their normal activity happens when you are not looking.