Nano Fish Care Guide — Small Freshwater Fish | Razz Aquatics

New to keeping nano fish? You're in the right place. At Razz Aquatics we specialize in small, peaceful freshwater fish that thrive in planted and nano aquariums. This guide covers everything you need to know to keep your nano fish healthy, active, and thriving.

1. What Are Nano Fish?

Nano fish are small freshwater fish — typically under 2 inches — that are well suited to smaller aquariums and planted tanks. They are generally peaceful, easy to care for, and work beautifully alongside freshwater shrimp and snails.

Types of Nano Fish We Carry

Rasboras Rasboras are shoaling fish that do best in groups of 6 or more. They are active, peaceful, and one of the most popular nano fish for planted tanks. The Celestial Pearl Danio and Chili Rasbora are customer favorites.

Tetras Tetras are colorful, hardy, and easy to care for. They are schooling fish that prefer groups of 6 or more. Ember Tetras and Green Neon Tetras are excellent choices for smaller tanks.

Corydoras Corydoras are peaceful bottom dwellers that help keep your substrate clean. They are social fish that do best in groups of 6 or more. Pygmy Corydoras are a great choice for nano tanks.

Loaches Loaches are active, curious fish that add personality to any tank. Kuhli Loaches and Dwarf Chain Loaches are popular choices for planted aquariums.

Plecos & Catfish Small pleco and catfish varieties are excellent algae eaters and cleanup crew. Otocinclus are a favorite for shrimp-safe planted tanks.

2. Tank Requirements

Tank Size

Most nano fish can thrive in tanks as small as 5–10 gallons, though larger is always better for water stability. A 20 gallon long is an excellent setup for a community nano fish tank.

  • 5–10 gallons — ideal for a single species of small rasboras or tetras
  • 10–20 gallons — great for a community of 2–3 species
  • 20+ gallons — best for a full planted community tank

Filtration

A sponge filter or hang-on-back filter works well for nano fish tanks. Make sure to add a pre-filter sponge over any intake to protect small fish and baby fish from getting sucked in.

Plants

Live aquatic plants are highly recommended for nano fish tanks. They provide hiding spots, reduce stress, and help maintain water quality. Great beginner plants include:

  • Anubias — easy, low light, attaches to driftwood and rocks
  • Java Fern — hardy, low light, great for background
  • Java Moss — excellent for fry to hide in
  • Stem Plants — fast growing, great for absorbing nitrates

Lighting

Most nano fish don't have specific lighting requirements. A standard aquarium light on an 8–10 hour cycle works well. If you're keeping live plants, choose a light rated for planted tanks.

3. Water Parameters

Nano fish are generally adaptable but do best in stable, well-maintained water. Here's a quick reference:

Parameter Recommended Range
Temperature 72–78°F
pH 6.5–7.5
GH 4–12 dGH
KH 2–8 dKH
Ammonia 0 ppm
Nitrite 0 ppm
Nitrate <20 ppm

Always cycle your tank before adding fish. The nitrogen cycle establishes beneficial bacteria that convert toxic ammonia and nitrite into less harmful nitrate. Adding fish to an uncycled tank is the number one cause of fish loss for new hobbyists.

4. Water Changes

Regular water changes are essential for keeping nitrates in check and maintaining a healthy environment for your nano fish.

  • Frequency — 20–30% water change once a week
  • Temperature — match the temperature of new water to your tank before adding
  • Dechlorinator — always treat tap water with a dechlorinator like Seachem Prime before adding to your tank
  • Slow and steady — add new water slowly to avoid shocking your fish

5. Feeding

Nano fish have small mouths and need appropriately sized food. Overfeeding is one of the most common mistakes — uneaten food decays and spikes ammonia.

What to feed:

  • High quality micro pellets or nano fish flakes
  • Frozen or live foods — baby brine shrimp, daphnia, and micro worms are excellent treats
  • Blanched vegetables — some species like zucchini and spinach

Feeding schedule:

  • Feed once or twice a day
  • Only as much as they can eat in 2–3 minutes
  • Remove any uneaten food after a few minutes

6. Compatible Tank Mates

Most nano fish are peaceful and do well with other small, non-aggressive species. Some excellent tank mate combinations:

  • Nano fish + shrimp — most nano fish are shrimp safe, especially with adult Neocaridina shrimp. Avoid larger, more predatory fish with shrimp.
  • Nano fish + snails — Nerite snails and Mystery snails make excellent tank mates
  • Multiple nano fish species — mixing Rasboras, Tetras, and Corydoras creates a beautiful, active community tank

Fish to avoid keeping with nano fish:

  • Cichlids — most are too aggressive
  • Bettas — can be aggressive toward small fish
  • Any fish large enough to eat your nano fish

7. Common Issues & How to Fix Them

Fish are hiding or inactive after arrival

Normal. Give them 24–72 hours to adjust to their new environment. Keep lights dim for the first day.

Fish loss after arrival

Almost always a water quality issue or acclimation problem. Test for ammonia and nitrite immediately. See our acclimation guide for proper introduction technique.

Fish not eating

Common in the first few days after arrival due to stress. Try offering frozen baby brine shrimp as an enticing food. If it continues beyond a week check your water parameters.

White spots on fish (Ich)

Ich is a common parasite that appears as white spots on fins and body. It is treatable — raise the temperature slowly to 82°F and treat with an ich medication. Remove any invertebrates before medicating as most ich treatments contain copper which is toxic to shrimp and snails.

8. Keeping Nano Fish with Shrimp

One of the most common questions we get is whether nano fish are safe with shrimp. The answer is — it depends on the species and the size of the shrimp.

Generally shrimp safe:

Use caution with:

  • Larger Tetras — may eat baby shrimp
  • Loaches — some species will eat small shrimp

Best practice — if keeping fish with shrimp, add plenty of moss and hiding spots so baby shrimp can take cover. Adult Neocaridina shrimp are generally too large for most nano fish to eat.

Ready to Stock Your Tank?

Browse our full selection of healthy, carefully sourced nano fish at Razz Aquatics. Every order ships with our 100% Live Arrival Guarantee and arrives in insulated packaging with a free heat or ice pack if needed.

Also read:

Questions? Reach out through our contact form — we're always happy to help.

— Razz Aquatics

Back to blog