Slender mudskipper

Where they come from

Slender mudskippers (Zappa confluentus) are the kind of fish that make you double-take because they are not really trying to be underwater fish. They come from coastal mudflats and mangrove edges where the tide comes and goes, leaving warm, shallow puddles, slick mud, and lots of air exposure.

Think brackish backwaters: shifting salinity, blazing sun, and a daily routine of crawling, perching, and hunting little critters on the surface. If you set the tank up like a normal aquarium, you will be fighting their nature the whole time.

Setting up their tank

This is more like building a tiny shoreline than setting up a fish tank. They need land, shallow water, and a way to get completely out of the water whenever they want. The water side is still brackish, filtered, and heated, but the land side is what makes or breaks the setup.

• Tank style: paludarium with a big land area (at least half the footprint as land is a good starting point).
• Footprint matters more than height. Wider and longer beats tall every time.
• Water depth: shallow (they are happy in a few inches / 8-15 cm), with gentle slopes so they can climb out easily.
• Land: sand/mud mix or fine sand with packed areas; add flat rocks and mangrove-like wood for perches.
• Salinity: brackish, mixed with marine salt (not freshwater 'aquarium salt'). Aim stable rather than chasing exact numbers.
• Filtration: gentle but capable. They are messy eaters, and leftover meaty food will foul water fast.
• Heat and humidity: warm water and warm air. A covered top helps hold humidity so they do not dry out during long basking sessions.
• Light: normal day/night cycle. If you use strong lights, give shaded spots so they can get out of the glare.

I like to build the land with stacked rock or egg-crate style supports, then cap it with sand so it does not collapse. Leave a few shallow pools and damp zones. They spend a lot of time in that in-between area where the sand is wet but not submerged.

What to feed them

They are little predators with a big appetite, and they prefer food they can grab and chew at the surface or on land. Most will ignore flakes and pellets unless they are trained from young, and even then, meaty foods get the best response.

• Staples: small crickets, roaches (tiny ones), fly larvae, earthworm pieces, blackworms, bloodworms, mysis, chopped shrimp.
• Occasional treats: small snails, tiny pieces of clam or fish, live ghost shrimp (in brackish they do fine for a bit).
• Feeding style: target feed with tweezers or drop food right at the waterline and on favorite perches.
• Schedule: small meals more often beats one huge dump of food. They will gorge and the leftovers will rot.

Watch for vitamin gaps if you lean hard on one frozen food. I rotate at least 3-4 different items. If they start getting picky, live foods usually reset their enthusiasm.

How they behave and who they get along with

Slender mudskippers have a lot of personality. They perch, posture, and will absolutely claim favorite spots. You will see head-bobbing and little shoving matches, especially around prime basking rocks and feeding areas.

• Best kept: species-only, especially while you are learning their rhythms.
• Group dynamics: more hiding spots and more 'good' perches reduces bullying. Watch for one fish pinning another away from the land area.
• Tankmates: most 'community brackish fish' are a mismatch because mudskippers want land access and they hunt anything small enough.
• Inverts: consider them food unless proven otherwise.

If you really want tankmates, think in terms of: can they handle the same salinity, will they stay in the water portion, and can they avoid being mistaken for lunch. Even then, you are adding stress and competition in a tank that already has a lot going on.

Breeding tips

Breeding mudskippers in home setups is possible in the broader group, but it is not a casual project. They typically use burrows and need the right substrate depth and structure, plus stable seasonal cues. With slender mudskippers specifically, most hobbyists do not stumble into breeding by accident.

• Deep, diggable substrate zones help (think several inches / 10+ cm in at least part of the land area).
• Keep humidity high and give them quiet. Constant disturbances or heavy tank maintenance can stop any courtship behavior.
• Watch for pair formation and one fish guarding an area. If you see repeated chasing in one corner and digging behavior, you may be getting close.
• If eggs or fry appear, expect them to be extremely vulnerable to tankmates and even other mudskippers.

Common problems to watch for

Most losses I have seen (and a couple close calls in my own tanks) come down to three things: escapes, dirty water from meaty foods, and the land area being wrong. These fish can handle a lot, but they do not handle the wrong kind of setup.

• Escape and desiccation: check the lid weekly, especially after maintenance.
• Skin issues and fin damage: often from fighting, rough decor, or too-dry air. Provide damp zones and smooth perches.
• Ammonia/nitrite spikes: common in new builds and after heavy feeding. They are messy and brackish tanks can cycle slower than people expect.
• Moldy, sour substrate: happens if the land stays waterlogged without ventilation or if food gets buried. Spot clean and do not overfeed.
• Incorrect salt: use marine salt mix. Plain sodium chloride does not give the buffering and minerals brackish setups usually need.
• Temperature swings: shallow water changes temperature quickly. Keep the room and tank stable.