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Sunday, March 25, 2007

Koi and Aluminum

I am in the process of building a larger pond for my koi. Is it safe to incorporate a cast aluminum urn into the design? My plan is to pump water from the biological filter up through the bottom of the urn where it will then splash over the sides of the urn and back into the pond. -Eric

You should be fine with using an aluminum urn if you have pH neutral or alkaline water. If your water is acidic, the aluminum urn will harm your fish. When aluminum is in acidic water, it seems to cause respiratory problems for fish. Here's an article from PumMed on Aluminum Toxicity to fish:

Aluminium is acutely toxic to fish in acid waters. The gill is the principal target organ and death is due to a combination of ionoregulatory, osmoregulatory and respiratory dysfunction. The toxic mechanism has hitherto received little direct consideration and is unknown. In this paper the mechanism of acute aluminium toxicity is approached from a chemical perspective. Symptomatic evidence of toxicity is taken from the literature and combined with our own research to elucidate a biochemically sound model to describe a possible mechanism of acute aluminium toxicity in fish. The proposed model delineates the chemical conditions immediately adjacent to the gill surface and emphasizes their importance in aluminium's toxic mode of action. The mechanism is shown to be bipartite. Aluminium binding to functional groups both apically located at the gill surface and intracellularly located within lamellar epithelial cells disrupts the barrier properties of the gill epithelium. The concomitant iono- and osmoregulatory dysfunction results in accelerated cell necrosis, sloughing and death of the fish. The mechanism of epithelial cell death is proposed as a general mechanism of aluminium-induced accelerated cell death.

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