(a) Specifications. Formalin is an aqueous solution containing approximately 37 percent by weight of formaldehyde gas, U.S.P.
(b) Sponsors. See sponsors in §510.600(c) of this chapter for uses as in paragraph (d) of this section.
(1) No. 050378 for use as in paragraph (d) of this section.
(2) Nos. 049968 and 067188 for use as in paragraphs (d)(1)(i), (ii), and (iii), (d)(2)(i), (ii), and (iii), and (d)(3) of this section.
(c) [Reserved]
(d) Conditions of use. It is added to environmental water as follows:
(1) Indications for use—(i) Penaeid shrimp. For control of external protozoan parasites Bodo spp., Epistylis spp., and Zoothamnium spp.
(ii) 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.
(iii) All finfish eggs: For control of fungi of the family Saprolegniaceae.
(iv) Freshwater-reared finfish. For the control of mortality due to saprolegniasis associated with fungi in the family Saprolegniaceae.
(2) Amount. The drug concentrations required are as follows:
(i) For control of external protozoan parasites on shrimp:
| Shrimp | Concentration of formalin (microliters per liter) | |
|---|---|---|
| Tanks and raceways (up to 4 hours daily) | Earthen ponds (single treatment) | |
| Penaeid Shrimp | 50 to 1001 | 252 |
1Treat for up to 4 hours daily. Treatment may be repeated daily until parasite control is achieved. Use the lower concentration when tanks or raceways are heavily loaded with phytoplankton or shrimp, to avoid oxygen depletion due to the biological oxygen demand created by decay of dead phytoplankton. Alternatively, a higher concentration might be used if dissolved oxygen is strictly monitored.
2Single treatment. Treatment may be repeated in 5 to 10 days if needed.
(ii) For control of external parasites on finfish:
| Aquatic species | Administer in tanks and raceways for up to 1 hour (microliter/liter or part per million (µL/L or ppm)) | Administer in earthen ponds single treatment (µL/L or ppm) |
|---|---|---|
| Salmon and trout: | ||
| Above 50 °F | Up to 170 | 15 to 251 2 |
| Below 50 °F | Up to 250 | 15 to 251 2 |
| All other finfish | Up to 250 | 15 to 251 2 |
1Use the lower concentration when ponds, tanks, or raceways are heavily loaded with phytoplankton or fish to avoid oxygen depletion due to the biological oxygen demand by decay of dead phytoplankton. Alternatively, a higher concentration may be used if dissolved oxygen is strictly monitored.
2Although the indicated concentrations are considered safe for cold and warm water finfish, a small number of each lot or pond to be treated should always be used to check for any unusual sensitivity to formalin before proceeding.
(iii) 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.
(iv) For the control of mortality in freshwater-reared finfish due to saprolegniasis associated with fungi in the family Saprolegniaceae: In tanks and raceways, administer 150 µL/L (ppm) for 60 minutes per day on alternate days for three treatments.
(3) 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.
[51 FR 11441, Apr. 3, 1986, as amended at 58 FR 59169, Nov. 8, 1993; 59 FR 60076, Nov. 22, 1994; 63 FR 38304, July 16, 1998; 68 FR 5563; Feb. 4, 2003; 72 FR 45158, Aug. 13, 2007; 76 FR 17339, Mar. 29, 2011; 79 FR 2786, Jan. 16, 2014; 82 FR 58556, Dec. 13, 2017; 84 FR 53311, Oct. 7, 2019]
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