Inirida F1 Altum Angelfish (Pterophyllum altum)

Inirida F1 Altum Angelfish (Pterophyllum altum) is a specialist true-altum listing for experienced aquarists. This is not the same fish as a hardy domestic Pterophyllum scalare angel: altums are taller, more sensitive to water swings and best kept in a mature aquarium planned around their height, warmth and calm behaviour.

The Inirida label matters because the Rio Inirida is part of the upper Orinoco drainage where true Pterophyllum altum occurs. F1 stock means first-generation captive-bred from wild-type parents, giving keepers the true altum look with better aquarium adaptation than freshly imported wild fish. This SKU is currently out of stock on live inventory, so use the page as a care and planning reference until availability returns.

Natural Range and Why It Changes the Care

FishBase places Pterophyllum altum in the upper Rio Negro and Orinoco systems, including Inirida and Atabapo tributaries. These habitats are warm, soft and often acidic, which explains why altums need a different setup from common angelfish. Their tall body and long fins evolved for moving among roots, branches and vertical structure rather than rushing through open current.

For aquarists, the practical lesson is stability. Altums can adapt to captive conditions, especially as F1 fish, but they dislike immature filters, sudden temperature changes, abrupt pH shifts and rough handling. Set the tank up before ordering, let the filter mature, and keep maintenance small and consistent rather than dramatic.

Aquarium Setup

Tank height is the first requirement. A shallow aquarium may hold the litres on paper but still cramp an adult altum. Plan at least 60 cm of water height, with more height preferred, and use a long footprint so a group can establish space without constant pressure. A juvenile can be grown on carefully, but the long-term plan should be a deep display, not a standard small community tank.

Use smooth vertical wood, root-style structure, broad-leaved plants and shaded areas. Flow should be clean and oxygen-rich without blasting the fish across the tank. Strong biological filtration is essential, but disperse the outlet with a spray bar or gentle return. Keep ammonia and nitrite at zero and nitrate low.

Water and Acclimation

Source references for true altums point to very soft, acidic water and warm temperatures. In the aquarium, aim for warm stable conditions, usually around 27-30 C, with soft water and pH in the acidic to mildly acidic range. Do not chase numbers daily if your fish are settled; sudden swings are more dangerous than a carefully maintained, consistent value.

Acclimation should be slow and calm. Dim the lights, match temperature carefully and avoid adding altums to a tank that has just been rescaped, medicated or cycled. Give them quiet time after introduction. Young altums may be cautious feeders at first, so make sure faster tank mates do not take every meal.

Feeding

Feed a varied, protein-rich menu built around quality cichlid pellets or granules plus frozen foods such as bloodworm, brine shrimp, mysis and daphnia. Offer modest portions and remove leftovers. Warm soft-water tanks can deteriorate quickly if uneaten food is left to break down, and altums are much less forgiving of poor water than many everyday community fish.

Tank Mates

Choose calm, warm-water companions that will not nip fins or compete aggressively for food. Larger peaceful tetras, suitable warm-water Corydoras, small plecos and other gentle South American species can work in a large enough aquarium. Avoid tiger barbs, serpae-type fin nippers, aggressive cichlids, boisterous bottom dwellers and tiny fish that may be eaten once the altums mature.

Groups of juveniles often settle better than pairs of unbonded fish, but a group needs space. As adults mature, watch for pair formation and territory pressure. If one pair begins to dominate most of the aquarium, be ready to separate or rehome fish rather than letting weaker individuals decline.

Similar Angelfish to Compare

If you want another true-altum style listing, compare Orinoco F1 Altum Angelfish and Dantume Altum Angelfish. For domestic angelfish forms that are usually easier to place in community aquariums, compare Rio Nanay Angelfish or Blue Angelfish.

Health Notes

Watch breathing rate, fin posture and feeding response during the first week. Clamped fins, hiding, heavy breathing or refusal to feed after settling time usually point to water quality, stress or tank-mate pressure. Quarantine is strongly recommended for premium cichlids, especially if they are joining an established display.