Heavy Metals in Aquarium Water

Heavy metals are elements that are toxic to aquatic life even at extremely low concentrations. Unlike Ammonia or Nitrite, they are rarely tested for by hobbyists, making them a hidden danger.

Common Heavy Metals

Copper (Cu)

• Sources: Old copper plumbing, some medications (Cupramine), anti-snail treatments.
• Toxicity: Lethal to invertebrates (Shrimp, Snails) at concentrations as low as 0.01 ppm. Fish can tolerate slightly more but suffer gill damage.
• Warning: If you ever treat a tank with copper medication, that tank is permanently unsafe for shrimp. Copper binds to silicone sealant and leaches indefinitely.

Zinc (Zn)

• Sources: Galvanized metal decorations, bolts, or clips accidentally placed in water.
• Toxicity: Causes respiratory failure in fish.

Lead (Pb)

• Sources: Old plumbing solder, some fishing weights used as plant anchors.
• Toxicity: Accumulates in tissue. Chronic low-level exposure stunts growth and damages organs.

Iron (Fe)

• Context: Iron is also a heavy metal, but in small, chelated amounts it is an essential plant nutrient. Overdosing liquid fertilizer can raise iron to toxic levels for sensitive fish.

How Heavy Metals Enter Your Tank

1. Tap Water: Older homes with copper or lead pipes can have measurable levels, especially in the first flush of the day.
2. Decorations: Non-aquarium-safe metals, painted ornaments, or corroded equipment.
3. Medications: Copper-based treatments for Ich or parasites.

Removal & Prevention

1. Run the Tap: Before using tap water, run it for 30-60 seconds to flush stagnant pipe water.
2. Water Conditioners: Products like Seachem Prime bind heavy metals into non-toxic complexes.
3. RO/DI Water: Reverse Osmosis removes 95%+ of heavy metals.
4. Activated Carbon: Absorbs some metals from the water column.
5. Tannins: Humic acids naturally chelate (bind) heavy metals, reducing their bioavailability.