AUSTRALIAN FRESHWATER CRAB 4.5-5cm

Australian freshwater crabs include a few native species suitable for aquariums, primarily from genera like Holthuisana (e.g., Freshwater Brown Back Crab) – A small, amphibious scavenger native to northern Australia’s inland rivers, often kept in freshwater home aquariums. These are hardy, interesting scavengers, but their care varies by species—some are more semi-aquatic, while others are fully aquatic. Scavengers; active, can be territorial or nippy toward slow/sick tankmates. Estuaries, inland rivers, billabongs, and shaded edges with detritus/vegetation across Australia (some tolerate varying salinities). Many are amphibious or climb out periodically. Many Australian species (e.g., Holthuisana) are semi-aquatic and benefit from an “island,” mangrove root, or sloped area to exit water for gill function. Fully aquatic Amarinus lacustris does not strictly need this. Some tolerate or prefer slightly brackish (5–15 ppt / SG 1.005–1.010) as they come from estuarine areas.

TANK SET UP: Minimum 30–40L per crab; larger is better, especially with tankmates. Provide plenty of hiding spots (rocks, caves, driftwood, leaf litter) and substrate for digging (sand or fine gravel preferred). Decorated with Live plants (e.g., for cover and biofilm) is excellent. Add leaf litter for natural foraging—excellent escape artists—secure lid essential.

TANK MATE: Best in species-only or with fast, larger fish (e.g., some cichlids or goldfish if parameters match). Avoid with small/shrimp/snails in most cases.

FILTRATION: Robust but gentle flow (they dislike strong currents). Canister, HOB, or sponge filters work; avoid ones that can damage or nibble excessively. Good biological filtration is key, as they are messy eaters. Plants help with natural filtration.

MAINTENANCE: 20–30% weekly or 10–25% every 2–4 weeks. Zero ammonia/nitrite; low nitrates. Sensitive to copper and poor water quality. They moult periodically—do not remove old exoskeleton (they eat it for calcium). Provide calcium sources (e.g., cuttlebone) if needed.

LIGHTING: Does not require strong or direct sunlight. However, the crab do need a consistent day/night light cycle (usually 12 hours on and 12 hours off) to maintain their natural biological rhythms and encourage healthy moulting. If you do use UVB, ensure it is a low-output bulb (7% or less) and that the crabs have plenty of places to hide from it. Or use a low-wattage, full-spectrum LED aquarium light.

FEEDING: Sinking pellets, algae wafers, blanched veggies (zucchini, spinach), occasional protein (bloodworms, etc.), and detritus/biofilm.