Biofilm: the first food for baby shrimp

Quick answer

Baby dwarf shrimp do not eat what the adults eat. They graze biofilm, the living film of bacteria, diatoms, algae and protozoa that coats every submerged surface in an established aquarium.

This is why shrimplets vanish in a clean, new, well-scrubbed tank and thrive in an older one that looks slightly untidy. The question is almost never what to feed the babies. It is whether the tank has enough surface for them to graze on before they are born.

Powdered foods matter, but they work by feeding the biofilm as much as by feeding the shrimp directly.

• Neocaridina and Caridina shrimplets hatch as miniature adults and start grazing immediately.
• A mature tank with plenty of grazing surface predicts survival better than any food you can buy.
• Feed the tank, not the shrimp. Powdered foods and botanicals grow the film the babies live on.
• Overfeeding is the fastest way to kill a shrimp colony, because shrimp are extremely sensitive to the water quality that decaying food destroys.
• Copper kills invertebrates. Check every medication, fertiliser and treatment before it goes near the tank.

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Copper is lethal to shrimp at concentrations that fish tolerate easily.

The usual sources are fish medications, particularly treatments for ich, velvet and external parasites, snail-killing products, some plant fertilisers, and tap water that has stood in copper plumbing. There is no safe way to treat a fish disease with a copper-based product in a tank containing shrimp, and copper adsorbs into substrate and silicone, so the tank can stay hostile after a water change. Read every label for copper, copper sulphate, cupric ion or chelated copper before it goes anywhere near the water.
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Decide in 60 seconds

Why biofilm is the answer

A shrimplet is a few millimetres long. It cannot chase food, cannot compete with an adult at a pellet, and cannot handle a particle of any size.

What it can do is walk across a surface with its mouthparts down, scraping. Every submerged surface in an established aquarium carries a thin living layer: bacteria bound in their own secretions, diatoms, single-celled algae, protozoa, and the organic matter caught in it. That layer is continuously renewed, spread across the entire tank, and available every minute of the day.

It is, in other words, exactly the food supply a tiny animal that cannot travel needs.

This also explains the single most consistent observation in the shrimp hobby: colonies do badly in new tanks and well in mature ones. A tank set up last month has clean glass, clean substrate and clean plants. There is nothing to graze.

The corollary is uncomfortable for tidy aquarists. Aggressive cleaning, scrubbing every surface, and replacing filter media removes the food supply. A shrimp tank should look a little lived in.

Building grazing surface before you need it

The work is done in the months before the first shrimplets, not after.

Mature the tank properly.

Give it time with plants growing and a stable cycled filter before adding shrimp, and longer still before expecting babies to survive. Weeks is optimistic; months is realistic.

Add surface area, not just volume.

Moss is the classic answer because it has an enormous surface area per unit of space and it also provides cover. Java moss and similar species are the standard, and a dense clump is a shrimplet nursery in its own right.

Use botanicals and leaf litter.

Indian almond leaves, alder cones, oak and beech leaves, cholla wood and similar botanicals slowly break down and support both biofilm and the microorganisms shrimp graze alongside it. Rinse and soak or boil them before adding, and let them decompose in place rather than removing them the moment they look ragged.

Use a sponge filter, or sponge the intake.

An open filter intake will remove shrimplets from the tank permanently. A sponge filter solves the problem and doubles as a large biofilm surface that shrimp graze constantly.

Do not sterilise.

Skip the scrubbing of every surface, keep some of the algae on the back glass, and do not replace all the filter media at once.

A tub of moss seeded from an established tank is one of the cheapest ways to bring grazing surface into a new one.

Feeding the tank rather than the shrimp

Powdered shrimp foods exist because they solve a specific problem: they disperse, settle across surfaces, and feed both the shrimplets directly and the biofilm they are grazing.

The technique that matters is restraint. A shrimp tank is a small volume with a heavy bioload of decomposition and no large animal to consume mistakes. Uneaten food does not disappear; it rots, drives up ammonia and nitrite, and shrimp are among the least tolerant animals in the hobby of both.

The workable rule is that food should be gone within a few hours, and that seeing shrimp graze on empty surfaces between feedings is normal and healthy rather than a sign of hunger.

Blanched vegetables such as courgette and spinach are widely used and are readily taken, but they foul quickly. Remove what is not eaten within a few hours, and be aware of pesticide residue on produce that was never intended for an aquarium.

Feeding days can be skipped. An established planted shrimp tank contains a continuous food supply, and colonies frequently do better with fewer feedings than with more.

A small mound that disappears within hours is right. A mound still there the next day is a water quality problem in progress.

Moulting, and why it fails

Shrimp have a rigid exoskeleton and grow by shedding it. A shrimplet moults frequently, because it is growing fast.

Moulting is a demanding, vulnerable event. The animal absorbs water to split the old shell, backs out of it, and then hides while the new one hardens. During that window it cannot defend itself and it is heavily dependent on the minerals dissolved in the water.

Failed moults are the classic sign of a mineral problem, and keepers commonly see one of two patterns. Either the shrimp cannot free itself and dies part-way out of the old shell, or a visible white gap appears at the join between the head shell and the body, with the animal unable to complete the separation.

The usual causes are the mineral content of the water being wrong for the species, and a sudden change in it. A large water change with water of a different hardness is a common trigger, which is why gradual changes and matched replacement water matter so much for shrimp.

Leave shed exoskeletons in the tank. Shrimp eat them and recover the minerals, and removing them is throwing away part of the supply.

Predation and the disappearing shrimplet

If babies appear and then are gone within days, feeding is often not the problem.

Fish.

Almost anything with a mouth large enough will eat shrimplets, including species marketed as peaceful community fish. A shrimp breeding tank is usually a shrimp-only tank, or one with a very carefully chosen exception.

Filter intakes.

Any powered filter with an open intake will remove shrimplets. Sponge over it or use a sponge filter.

Hydra and planaria.

Both arrive on plants and both are a threat to very small shrimp. Treating for them in a shrimp tank is difficult because most treatments are also toxic to shrimp, so prevention through quarantining new plants matters more than treatment does.

Nowhere to hide.

A bare tank offers no refuge. Dense moss and leaf litter reduce losses independently of feeding.

The routine that produces a colony

What never to do

Do not use any copper-containing medication, fertiliser or snail treatment in a tank with shrimp. Move the fish out and treat it elsewhere.

Do not do large or rapid water changes. Shrimp tolerate a wide range of stable conditions and very little sudden change.

Do not add shrimp to a new tank without drip acclimation. A rapid transfer into different water is a common cause of losses in the first days.

Do not scrub the tank clean before a batch of shrimplets is due. You are removing their food.

Do not keep adding food because you cannot see the shrimplets. They are small, they hide, and the food you add to reassure yourself is what poisons the tank.

Do not assume Amano shrimp will breed the same way. Their larvae need brackish water and will not survive in a freshwater aquarium, so a berried Amano is not a colony in the making.

Do not add fish to a breeding tank and hope. Almost all of them will eat the babies.

When to get help

Shrimp are rarely seen by a general veterinary practice, so the people to ask are an aquatic veterinarian where one is available, or an experienced dwarf shrimp keeper or specialist retailer.

Get advice quickly for a run of failed moults, for sudden adult deaths, or for any suspicion that a copper-containing product has entered the tank.

Test the water first in every case. Ammonia, nitrite, nitrate, and the mineral parameters for your species tell an experienced keeper more than a description of the behaviour does.

The goal is a tank where shrimp of every size are grazing on surfaces, and where you rarely need to feed at all.