Specifications. Formalin is an aqueous solution containing approximately 37 percent by weight of formaldehyde gas, U.S.P.

Sponsors. See Nos. 049968, 050378, and 067188 in § 510.600(c) of this chapter.

[Reserved]

Conditions of use. It is added to environmental water as follows:

Indications for use. (i) Penaeid shrimp. For control of external protozoan parasites Bodo spp., Epistylis spp., and Zoothamnium spp.

All finfish. For control of external protozoa Ichthyophthirius spp., Chilodonella spp., Ichthyobodo spp., Ambiphrya spp., Epistylis spp., and Trichodina spp., and the monogeneans Cleidodiscus spp., Gyrodactylus spp., and Dactylogyrus spp.

All finfish eggs: For control of fungi of the family Saprolegniaceae.

Amount. The drug concentrations required are as follows:

For control of external protozoan parasites on shrimp:

For control of external parasites on finfish:

For control of fungi of the family Saprolegniaceae on finfish eggs: Eggs of all finfish except Acipenseriformes, 1,000 to 2,000 µL/L (ppm) for 15 minutes; eggs of Acipenseriformes, up to 1,500 µL/L (ppm) for 15 minutes. A preliminary bioassay should be conducted on a small subsample of fish eggs to determine sensitivity before treating an entire group. This is necessary for all species because egg sensitivity can vary with species or strain and the unique conditions at each facility.

Limitations. Fish tanks and raceways may be treated daily until parasite control is achieved. Pond treatment may be repeated in 5 to 10 days if needed. However, pond treatments for Ichthyophthirius spp. should be made at 2-day intervals until control is achieved. Egg tanks may be treated as often as necessary to prevent growth of fungi. Do not use formalin which has been subjected to temperatures below 40 °F, or allowed to freeze. Treatments in tanks and raceways should never exceed 1 hour for fish or 4 hours for penaeid shrimp (even if they show no sign of distress), nor should it exceed 15 minutes for fish eggs. Do not apply formalin to ponds with water warmer than 27 °C (80 °F), when a heavy bloom of phytoplankton is present, or when the concentration of dissolved oxygen is less than 5 milligrams per liter.