Plants make a goldfish tank look better. They also give your fish something to explore. But there’s one more big reason to add plants: they help lower nitrate.
Why Plants Help With Nitrate
Goldfish make a lot of waste. Good bacteria in your tank turn that waste into nitrate. Water changes are still the best way to remove nitrate. But plants can slow down how fast nitrate builds up.
Here’s how plants help:
- They soak up nitrate straight from the water.
- They also soak up ammonia before it even turns into nitrate.
Fast-growing plants pull out more nitrogen than slow ones. That’s because they use it to grow new leaves, stems, and roots.
The Four Plant Types, Ranked
- Floating plants – very high nitrate control
- Houseplants with roots in the water – high nitrate control
- Fast-growing stem plants – medium to high nitrate control
- Rooted plants – low to medium nitrate control
This is just a general guide, not a strict rule. A big, healthy pothos plant can out-clean a few floating plants. A thick clump of hornwort can out-clean one small pothos cutting. Size and health matter more than type alone.
1. Floating Plants
These plants float on top of the water. Their roots hang down into the tank.
Common floating plants:
- Frogbit
- Salvinia
- Red root floaters
- Water lettuce
- Duckweed
Nitrate control: Very High
Floating plants get tons of light and easy access to air. This helps them grow fast. Their roots also sit right in the water, soaking up nitrogen as they go.
Duckweed grows especially fast and pulls in a lot of nitrogen.
But here’s the catch: the nitrogen only leaves your tank when you scoop out extra plants. If the plants die and rot in the tank, the nitrogen just goes right back into the water.
Two problems with floating plants:
- Goldfish love to eat them, especially duckweed. Sometimes the fish eat them faster than they can grow back.
- They don’t like rough water. Strong filters and splashing can hurt them or push them under.
Fix: Use a floating plant corral. This gives the plants a calm, protected spot. Just leave part of the surface open so air can still reach the water.
2. Houseplants With Roots in the Water
Some regular houseplants can grow with just their roots in the tank. Their leaves stay above the water. These are called emergent plants.
Popular choices:
- Pothos
- Heartleaf philodendron
- Monstera
- Syngonium
- Peace lily
- Spider plant
Nitrate control: High
These plants get the best of both worlds. Their roots pull nitrogen from the water. Their leaves get all the air and light they need above the tank.
A brand-new cutting won’t do much at first. But a big, healthy pothos with lots of leaves and roots can be one of your best tools for nitrate control.
Important: Only the roots should touch the water. If the leaves or stems get wet, they can rot.
Before you add a houseplant:
- Wash off all the dirt from the roots.
- Rinse the roots well.
- Check for fertilizer pellets or bugs.
- Attach the plant so its roots reach the water.
- Keep the leaves above the waterline.
Goldfish may nibble on the roots, so bigger plants usually do better than small cuttings. You can hold the plant in place with a basket, a filter compartment, a suction cup holder, or a hole in the lid.
Trim off any dead roots or yellow leaves right away. Rotting plant parts release nitrogen back into the tank.
3. Stem Plants
These plants grow straight up from a long stem, with leaves along the way. You can trim them and replant the cuttings.
Common stem plants:
- Hornwort
- Anacharis
- Water sprite
- Hygrophila
- Bacopa
- Ludwigia
Nitrate control: Medium to High
These plants grow fast, so they use up a lot of nitrogen. Hornwort, anacharis, water sprite, and Hygrophila are some of the best choices.
The hard part is keeping enough of them alive. Goldfish love to dig them up, tear them apart, and eat the new growth.
Tips for keeping stem plants safe:
- Plant them in thick clusters.
- Weigh them down with aquarium-safe plant weights.
- Tuck them behind rocks or driftwood.
- Grow them in weighted pots.
- Let them grow in for a while before adding goldfish.
You can also let hornwort and anacharis just float. This stops goldfish from digging them up, though the fish may still nibble on them.
A big, healthy clump of stem plants can really slow down nitrate. A few torn-up stems won’t do much.
4. Rooted Plants
These plants grow straight in the gravel or sand at the bottom of the tank.
Popular rooted plants:
- Amazon swords
- Cryptocoryne
- Vallisneria
- Dwarf aquarium lilies
- Tiger lotus
- Crinum
Nitrate control: Low to Medium
These plants get a lot of their food from the substrate (the gravel or sand), not just the water. So they don’t clean the water quite as well as other plant types.
Fast growers like Vallisneria help more than slow growers like Cryptocoryne.
Rooted plants look great and add a nice permanent feel to the tank. But don’t count on them as your main nitrate fighter. Let the faster plants do the heavy lifting.
Protect Rooted Plants With Pebbles
Goldfish love to dig, and that means newly planted plants get uprooted easily.
Here’s a simple fix:
- After planting, place a loose ring of smooth pebbles around the base.
- The pebbles add weight and make it harder for goldfish to dig there.
- Use pebbles too big for your goldfish to swallow.
- Avoid sharp stones that could hurt their fins.
- Don’t pile pebbles on the plant’s crown (where the leaves meet the roots). This can cause rot.
This trick works great for:
- Amazon swords
- Cryptocoryne
- Vallisneria
- Tiger lotus
Another option: Plant it in a terracotta pot, then top it with smooth pebbles. This keeps goldfish from digging it up.
Many rooted plants also do better with root tabs, especially in sand or gravel that doesn’t have many nutrients.
A Note About Anubias and Java Fern
These plants have a thick stem called a rhizome. Never bury it — it can rot.
Instead, tie or glue these plants to:
- Rocks
- Driftwood
- Aquarium decorations
Anubias has tough leaves that goldfish usually leave alone. But it grows very slowly, so it doesn’t help much with nitrate. Keep it around for looks, not for cleaning the water.
Quick Comparison
| Plant type | Nitrate control | Goldfish-proof? | Best thing about it | Biggest downside |
|---|---|---|---|---|
| Floating plants | Very high | No | Grows super fast | Gets eaten, hates rough water |
| Houseplants (roots in water) | High | Yes, if secured | Steady long-term help | Small cuttings take time |
| Stem plants | Medium to high | No | Fast underwater growth | Easily uprooted or eaten |
| Rooted plants | Low to medium | Somewhat, if protected | Looks permanent | Relies on substrate for food |
| Anubias/Java fern | Low | Yes | Tough and goldfish-safe | Grows very slowly |
The Best Setup Combines a Few Types
Instead of picking just one kind of plant, mix a few together:
- Floating plants for fast nitrogen removal
- A mature pothos for steady long-term help
- Hornwort or anacharis for fast underwater growth
- Vallisneria or swords, protected with pebbles
- Rooted plants in terracotta pots
- Anubias tied to rocks for a tough, goldfish-safe look
This gives you fast cleanup power plus a stable, good-looking tank.
Plants Help — But They Don’t Replace Water Changes
Plants are a great tool, but they’re not a replacement for regular tank care. Goldfish make a lot of waste, and plants can’t remove everything. Keep testing your nitrate and doing water changes, even with a tank full of plants.
To get the most out of your plants:
- Pick fast-growing species
- Give them the right amount of light
- Keep enough plant mass in the tank
- Protect new growth from hungry goldfish
- Remove dead leaves right away
- Trim and remove healthy extra growth often
- Keep testing your water and changing it regularly
Trimming matters a lot. Every time you remove healthy plant growth, you’re removing the nitrogen stored inside it — for good.
No plant is 100% goldfish-proof. The best plants are simply the ones that grow well in your tank and survive your goldfish’s curiosity. With the right mix of floating plants, houseplants, stem plants, and protected rooted plants, your goldfish tank can look great and stay a lot cleaner too.