What it involves day to day

Most days the job takes five minutes: feed the fish, check that water is flowing into the bed and draining back, and look over the leaves. Once a week you test the water, top up what evaporated and pick what is ready. The first six weeks are different. Before any fish go in, you run the system empty and feed the bacteria by hand until they can keep up with fish waste, and that wait is the part most people try to skip. After that the system mostly runs itself, and the work becomes reading small signs: fish that hang at the surface, a leaf that yellows, a reading that drifts.

A small orange goldfish swimming in a bare glass tank, with two more goldfish out of focus behind it — Small goldfish in a bare tank

The loop, and the five readings that tell you it is working

Ammonia

Fish release it through their gills and waste. It is toxic to them, and a healthy system reads 0.

Nitrite

The first group of bacteria turns ammonia into nitrite, which is also toxic. It should read 0 too.

Nitrate

A second group of bacteria turns nitrite into nitrate, which fish tolerate and plants feed on. A reading between 5 and 80 parts per million means the plants have food.

Acidity (pH)

Fish and bacteria like it above 7 and plants like it below, so aim for the overlap of 6.4 to 7.0. It drifts down over the months as the bacteria work.

Temperature

65 to 75 F suits goldfish, lettuce and the bacteria at once, which is ordinary room temperature.

A small glass tank on a dark table, lit from above, with green plants growing up past the waterline

Where it goes and what to check before you buy

A sturdy stand, an outlet and no direct sun

Weight

A filled 10-gallon tank with a wet pebble bed on top weighs about 130 pounds. It needs a level, sturdy stand or table, not a shelf.

Placement

Within reach of a grounded outlet, away from heating vents, and out of direct sun on the glass, which grows algae fast.

Bed size

Look for a grow bed about as large as the top of the tank and 3 to 8 inches deep. A bed much smaller than the tank cannot filter for the fish below it.

Pump

It should move the whole tank volume through the bed about once an hour. A tank-top kit includes one sized for the job, on a timer that floods the bed and lets it drain.

Tank shape

Tank-top beds are built for the standard 20 by 10 inch footprint, so buy the plain rectangular tank and skip bowfront or hexagon shapes.

From empty tank to first harvest

The cycle explained in full, free

Oklahoma State University Extension: Nitrification and Maintenance in Media Bed Aquaponics Free fact sheet on starting the bacteria with or without fish, what to test and how to keep a pebble bed healthy

What you can have going in your first month

A running loop

The tank filled, the pump lifting water into the pebble bed and a steady trickle draining back, with no leaks for a full week.

Seedlings in starter plugs

Lettuce and basil sprout within a week on a bright windowsill and are ready to move into the pebbles two weeks later.

A cycling chart

Test readings written down every other day that show ammonia falling, nitrite rising and then nitrate appearing, which is the bacteria colony arriving.

A planted bed

Once nitrate shows on the test, the seedlings go into the pebbles and start growing on it while the cycle finishes.

What to stock and what to plant

Fish

Two or three small fancy goldfish suit a 10-gallon system at room temperature. They are hardy and produce plenty of plant food, but they grow, so expect to move them to a bigger tank within a year or two.

Stocking limit

Three is the ceiling for 10 gallons. More fish make more plant food but leave less margin when a pump stops or a reading spikes.

First plants

Leaf lettuce, basil, mint, chives, parsley and watercress grow well on the modest nitrate a small tank makes.

Plants to hold off on

Tomatoes, peppers and cucumbers need far more nutrients than a few goldfish supply, so save them for a larger system.

Feeding

The fish food is the only fertilizer in the system. Yellow leaves with green veins on new growth point to low iron, the one nutrient fish food does not supply enough of.

A close-up of frilly green loose-leaf lettuce filling the frame — Loose-leaf lettuce

What trips beginners up

The wait

Four to six weeks of testing an empty tank feels like nothing is happening. Adding fish early is the most common way to lose them.

Slow early growth

A new system has little nitrate, so the first planting grows slower than seed packets promise. It speeds up by the third month.

Cloudy water and algae

Both are normal in the first weeks and usually clear on their own once plants and bacteria compete for the same nutrients.

Overfeeding

Uneaten food rots into ammonia faster than the bacteria can clear it. If food is left after two minutes, feed less.

Chasing numbers

Correcting acidity by more than 0.2 a day, or with products not made for fish tanks, harms the fish more than the drift did.

Scrubbing the bed

The brown film on the pebbles is the bacteria colony. Rinsing the bed in tap water or cleaning it out sends you back to week one.

Sprays and soaps

Houseplant insecticides, soapy hands and copper-based treatments all end up in the fish water. Pick pests off by hand.

Water, electricity and food you can eat

Outlets

Plug the pump, air pump and light into a GFCI outlet, and let every cord hang in a loop below the outlet so drips fall off before they reach the plug.

Hands

Wash them after working in the tank and before picking, and keep open cuts out of fish water.

Produce

Fish water should reach roots only. Wash everything you harvest, and throw out leaves that have dipped into the tank.

Fish

Never release fish or tank water into a pond, stream or storm drain. Goldfish are an invasive species in North American waters.

Food fish later

Tilapia and some other food fish need a permit or are banned in several states, so check with your state wildlife agency before sizing up.

A long-finned orange goldfish turning just below the waterline of an aquarium — A long-finned goldfish

Where to learn more

Extension fact sheets

State university extension services publish free, tested guidance on starting the bacteria and maintaining a pebble bed.

The standard manual

The UN Food and Agriculture Organization's free guide to small-scale aquaponics covers the chemistry, fish health and plant care in depth.

Other growers

Online communities are the fastest way to get a second opinion on a test reading or a sick plant, and local aquarium clubs know your tap water.

Free references and communities

A close-up of porous brown expanded clay pebbles around the base of a plant

How the shopping list is built

The grow bed is most of the bill

The essentials are one complete small loop: a 10-gallon tank, a grow bed kit that sits on top of it and brings its own pump, timer and clay pebbles, and the supplies for the fishless cycle (dechlorinator, ammonia and a liquid test kit, which you keep using every week afterward). The grow bed is most of the bill. Seeds, starter plugs and fish food are small costs, and the fish themselves come last, from a local store. The recommended lines fix the things that most often go wrong in a first system: an air stone for oxygen, a grow light for rooms without a sunny window, a thermometer and a net. The optional lines are for later problems and can wait until you see them.

Build the loop

Compare the options on each line, then set your tiers and check out from the cart. Clicking a card selects it there, and clicking the selected card again takes that line out. The first line, the fish, is not something you buy online. The two optional lines start out of the kit.

Goldfish

Essential · Livestock

The fish are the engine of the system: their waste is the only plant food it gets.

Not sold on Amazon · buy from a local fish store

Not sold on Amazon. Listed first because the whole kit is sized around them, but buy them last: two or three small fancy goldfish from a local fish store, once the tank reads 0 ammonia and 0 nitrite. Pick active fish with clear eyes and whole fins. Expect $2 to $10 each.

10-gallon aquarium

Essential · Core equipment

The fish live here and the grow bed sits on its rim. Ten gallons is the smallest volume that stays stable enough for a beginner.

budget

Marina LED Aquarium Kit, 10 gallon

4.5(1238)

$62.07

Only 12 left in stock - order soon.

Aquaponics

What it involves day to day

The loop, and the five readings that tell you it is working

Where it goes and what to check before you buy

From empty tank to first harvest

What to stock and what to plant

What trips beginners up

Water, electricity and food you can eat

Where to learn more

How the shopping list is built

Build the loop

Goldfish

10-gallon aquarium

Tank-top aquaponic grow bed kit

Freshwater liquid test kit

Water dechlorinator

Ammonia for fishless cycling

Goldfish food pellets

Loose-leaf lettuce seeds

Culinary herb seeds

Seed starter plugs

Aquarium air pump with air stone

Clip-on LED grow light

Aquarium thermometer

Small fish net

Chelated iron supplement

Bottled nitrifying bacteria