By Sophie Harding
What a planted tank needs — and why Amano shrimp are the answer
Every planted aquarium that runs for more than a few months develops algae. This is biology, not failure: photosynthetic organisms in a warm, lit, nutrient-rich environment will grow. The question is which organisms dominate.
The three algae types most UK planted tanks fight are: green hair algae, green thread algae, and diatom film. Plecos ignore them. Otocinclus eat a little diatom film. Cherry shrimp graze biofilm but mostly avoid structured algae. The species that genuinely eats all three, reliably, is Caridina multidentata — the Amano shrimp.
An Amano shrimp showing the diagnostic dotted line running along the flank — the key identification feature separating Caridina multidentata from similar-looking species like Caridina babaulti. Photo: Tropical Fish Co warehouse.
I'm Sophie Harding, the site's shrimp specialist. I keep Amanos in three of my twelve species tanks — they're the maintenance layer in my breeder planted tanks, quietly controlling algae between water changes.
The amphidromous life cycle — why you can't breed them
This is the single most important biological fact about Amano shrimp, and almost every UK hobby guide skips it.
Caridina multidentata is amphidromous: its life cycle requires movement between freshwater (where adults live) and brackish water (where larvae develop). The seminal lab work on this was done by M. Tsuda in 1990 [2].
What happens in the wild:
- Adult females release larvae into freshwater streams
- Larvae drift downstream in the current to coastal estuaries
- Larvae need brackish water (roughly 1.015 specific gravity, equivalent to 25% seawater) to complete four developmental moults
- After metamorphosis, juveniles migrate upstream back to freshwater
- Juveniles become adults in freshwater streams and the cycle repeats
What happens in your aquarium:
- Adult females release larvae into freshwater
- Larvae have no estuary to drift to
- Larvae die within 3–5 days
There is no way to breed Amanos in a standard aquarium setup. Specialist hobbyists have succeeded with a separate brackish rearing tank but it's a significant project — not a casual outcome of keeping the species.
Commercial stock comes from either wild-caught Japanese and Taiwanese specimens or farm-bred operations that maintain the brackish larval stage in dedicated hatcheries. Every Amano in the UK trade has been through one of these two supply chains [1].
Amano vs cherry — picking the right shrimp for your goal
Head-to-head: Amano vs Cherry
| Attribute | Amano Shrimp | Cherry Shrimp |
|---|---|---|
| Scientific name | Caridina multidentata | Neocaridina davidi |
| Adult size | 3–5 cm | 2–3 cm |
| Primary diet | Hair + thread algae | Biofilm |
| Breeds in freshwater | No | Yes (easily) |
| Colour variability | Mostly grey-brown (rare strains) | 12+ colour strains |
| Group size for function | 5–10 per 90 L | 10+ for colony |
| UK tap water tolerance | Moderate (6.5–7.8 pH) | Wide (6.5–8.0 pH) |
| Primary role | Algae control | Colony + colour |
| Lifespan | 2–3 years | 1.5–2.5 years |
| Price per shrimp (UK 2026) | £5–£15 | £2–£10 |
The planted-tank answer: keep both. A 90 L planted tank with 9 Amanos + 20 cherries is a complete shrimp crew — Amanos control hair algae, cherries graze biofilm and breed to sustain the colony. The species don't interbreed (different genera), so the tank stays genetically stable.
What Amanos actually eat — field observations
From my own tanks and from the observational research community [8], here's the realistic rank of what Amanos will and won't graze:
Will happily eat:
- Green hair algae
- Green thread algae
- Staghorn algae (moderately)
- Diatom film on glass and plants
- Leftover fish flakes + sinking pellets
- Dead plant matter
- Blanched vegetables (courgette, spinach)
- Sinking shrimp wafers
Occasionally nibble:
- Black beard algae (BBA) — rarely; don't rely on them
- Green spot algae
- Soft algae on driftwood
Ignore completely:
- Cyanobacteria (blue-green algae) — you need a 3-day blackout to kill this
- Hard, crusty algae on rocks
- Healthy plant tissue
The single best supplementary food
Once your tank is algae-clean, Amanos still need something to graze. The go-to supplement is a sinking shrimp wafer (Shrimp King, Hikari Shrimp Cuisine, or Bacter AE) — 2–3 times a week, one wafer per 10 Amanos. Drop at lights-out; the shrimp emerge from plant cover to feed.
Habitat in the wild — what their stream looks like
Amano shrimp side view. The dotted line pattern is the diagnostic — slightly compressed to a dashed pattern in younger specimens, becoming more distinct with age. Photo: Tropical Fish Co warehouse.
Caridina multidentata inhabits fast-flowing streams on the Japanese and Taiwanese islands and parts of mainland China, typically within 50 km of the coast (because of the amphidromous life cycle). Natural streams:
- Substrate: smooth river pebbles, some sand
- Flow: moderate to fast; well-oxygenated
- Temperature: 15–25 °C seasonal range (hence their tolerance of unheated UK tanks)
- pH: slightly alkaline (7.2–7.8) due to mineral-rich catchment geology [1]
- Vegetation: streamside mosses, submerged hardy plants (anubias-like species in tropical regions)
For an aquarium that mimics this habitat:
- Smooth river gravel or fine sand substrate
- Moderate flow from sponge or gentle canister filter
- Room temperature tank (no heater needed in most UK homes)
- Any planted tank layout — they're not biotope-purists
Stocking table — how many Amanos per tank size
One of the most common mistakes we see: buyers order "a couple" of Amanos for a 60 L planted tank and wonder why the algae keeps growing. The right stocking ratio is higher than most UK sources suggest.
| Tank volume | Amanos for light algae control | For a BBA-prone or high-light tank |
|---|---|---|
| 30 L nano | 3 | 4 |
| 60 L planted | 5 | 7 |
| 90 L planted | 8 | 10 |
| 120 L planted | 10 | 14 |
| 180 L planted | 15 | 20 |
| 240 L planted | 20 | 25 |
One Amano per ~8–10 L of planted-tank volume is the working algae-control ratio. Less = incomplete control. Much more = food-competition stress.
Algae-type table — what Amanos will and won't touch
| Algae type | Amano effectiveness | Alternative biological control |
|---|---|---|
| Green hair algae | ✓ Primary target | — |
| Green thread algae | ✓ Primary target | — |
| Green spot algae (dot pattern) | Partial grazing | Nerite snails, bristlenose pleco |
| Diatom film (brown glass coat) | Partial grazing | Otocinclus, nerite snails |
| Staghorn algae | Moderate grazing | Siamese algae eater |
| Black beard algae (BBA) | ✗ Rarely | Only Siamese algae eater [3] |
| Cyanobacteria / blue-green | ✗ None | 3-day blackout treatment |
| Hair algae on plant edges | ✓ Excellent | — |
| Leftover fish flakes + detritus | ✓ Excellent scavenger | Any bottom-dweller |
Use this table when planning an algae crew. For a fully- controlled planted tank: Amanos (hair/thread) + bristlenose pleco (green spot) + Siamese algae eater (BBA) covers every category.
Size-selection table — what you're actually buying
| Size in shop tank | Age | Resilience | Survival on first 14 days |
|---|---|---|---|
| Under 2 cm | Juvenile | Fragile | ~85% in stable tank |
| 2–2.5 cm | Sub-adult | Moderate | ~92% |
| 2.5–3.5 cm | Adult | Best | ~99% |
| 3.5+ cm | Mature adult | Best | 99%+ but ages out sooner |
If shops are selling under-2-cm Amanos at adult prices, they got a cheaper juvenile import and are pricing at adult market rates. Ask for larger grade if possible.
Watch: Amano shrimp grazing in a mature planted tank
Tank setup + welfare protocol
The 5 things an Amano tank needs
- 60 L minimum for a functional group of 5 Amanos
- Sponge filter or canister with pre-filter sponge to prevent juvenile shrimp being sucked into intakes
- Live plants — at least 30% plant coverage for hiding and grazing surface
- Stable parameters — weekly 10–20% water changes, no sudden shifts
- No known shrimp predators — no puffers, no large gouramis, no adult angelfish
Our welfare-first shipping protocol
- APHA-compliant live-animal carrier (licensed live-animal courier)
- Insulated polystyrene box with temperature-matched heat/cool packs by season
- Oxygen-charged double bags with air-space sized for 36-hour transit minimum
- Species-isolated quarantine for 7 days minimum before shipping
- Live Arrival Guarantee — photograph unopened bag within 2 hours, full refund/replacement [6]
The thing we explicitly don't do: ship via Royal Mail. It's not regulated for live animals; casualty rates on Royal Mail shrimp shipments run 30–50%. Any UK seller using Royal Mail is operating outside the APHA framework.
UK community + resources
The amano-shrimp community in the UK is smaller than the cherry-shrimp community but more technical:
- UK Aquatic Plant Society (UKAPS) — amano husbandry is a regular topic in the shrimp subforum
- Aqua Design Amano UK distributors — carry the ADA books where Takashi Amano's philosophy is documented [4]
- Facebook "UK Planted Tank Keepers" — Amano sightings in aquascape contest posts
- Practical Fishkeeping — features Amanos regularly in aquascape spotlights [7]
When your Amano shrimp arrive
Amanos ship better than cherries because of their larger body size and slower osmoregulation rate. Our standard protocol:
- Open in a dim, quiet room
- Float the sealed bag for 20 minutes — temperature equalisation
- Drip-acclimate for 60 minutes at 1 drop per second — slower than fish, matches shrimp osmoregulation
- Net into the tank (don't pour bag water into the display)
- Lights off for 2 hours
- No feeding for 24 hours — Amanos will start grazing existing algae within hours
First-week survival on our Amano shipments over the last 12 months: 99.6%.
Ready for more?
For cherry shrimp care alongside Amanos, see our cherry shrimp guide. For the fish-based algae specialist (black beard algae control), the Siamese algae eater guide.
The amano shrimp care guide covers breeding attempts (specialist project) + long-term colony management. Broader invertebrate husbandry is in the shrimp keeping care guide.
Full range: shrimps & crustaceans hub.
