The extensive use of antibiotics and various chemical compounds has resulted in drug residue and resistant pathogens in treated fish. Drug residue not only pollutes the environment, but also threatens human consumers. In contrast, garlic as a well‐known natural antibiotic that causes no environmental or physical side effects has shown to be effective for the treatment of many diseases in humans and animals owing to its antimicrobial, antioxidant, and antihypertensive properties. In aquacultural operations, garlic with dose optimization is strongly recommended. This review focuses on the application of garlic in various fish diseases treatments and the prospects of using garlic preparations in aquaculture.

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This study was conducted to investigate the effects of dietary propolis supplementation on growth performance, immune responses, disease resistance and body composition of juvenile eel, Anguilla japonica, in order to evaluate its bioavailability as a feed additive for this species. A total of 540 fish averaging 7.7 ± 0.22 g (mean ± SD) were randomly distributed into 18 tanks in groups of 30, and each tank was then randomly assigned to one of three replicates of six diets containing 0 (P 0 ), 0.25 (P 0.25 ), 0.5 (P 0.5 ), 1.0 (P 1 ), 2.0 (P 2 ) and 4.0 (P 4 ) % dietary propolis. At the end of 12 weeks of feeding trial, weight gain (WG), specific growth rate (SGR), feed efficiency (FE) and protein efficiency ratio (PER) of fish fed P 0.5 diet were significantly higher than those of fish fed P 0 , P 1 , P 2 and P 4 diets (P \ 0.05). These parameters were 148.9%, 0.72% day -1 , 94.4% and 2.9, respectively for fish fed P 0.5 diet. Serum lysozyme activity of fish fed P 0.5 (105.7 units mL -1 ) and P 1 (106.0 units mL -1 ) diets were significantly higher than those of fish fed P 0 , P 0.25 , P 2 and P 4 diets. Mucus lysozyme activity of fish fed P 1 (8.4 units 10 cm -2 ) diet was significantly higher than those of fish fed P 0 , P 2 and P 4 diets. Results indicated that the optimum dietary propolis supplementation levels could be 0.25-0.5% for optimum growth and feed efficiency, and 0.5-1% for enhanced immune responses and disease resistance in eel, A. japonica. This study may suggest that the dietary propolis level for the optimum immune responses could be higher than the level for the optimum growth of eel.

An environmental assessment was made of Alabama channel catfish Ictalurus punctatus farming which is concentrated in the west‐central region of the state. There are about 10,000 ha of production ponds with 10.7% of the area for fry and fingerlings and 89.3% for food fish. Food fish production was about 40,800 tons in 1997. Watershed ponds filled by rainfall and runoff make up 76% of total pond area. Water levels in many of these ponds are maintained in dry weather with well water. The other ponds are embankment ponds supplied by well water. Harvest is primarily by seine‐through procedures and ponds are not drained frequently. The main points related to Alabama catfish farming and environment issues are as follows: 1) catfish farming in Alabama is conservative of water, and excluding storm overflow, about two pond volumes are intentionally discharged from each pond in 15 yr; 2) overflow from ponds following rains occurs mostly in winter and early spring when pond water quality is good and stream discharge volume is high; 3) total suspended solids concentrations in pond effluents were high, and the main sources of total suspended solids were erosion of embankments, pond bottoms, and discharge ditches; 4) concentrations of nitrogen and phosphorus in effluents were not high, but annual effluent loads of these two nutrients were greater than for typical row crops in Alabama; 5) ground water use by the industry is about 86,000 m3/d, but seepage from ponds returns water to aquifers; 6) there is little use of medicated feeds; 7) copper sulfate is used to control blue‐green algae and off‐flavor in ponds, but copper is rapidly lost from pond water; 8) although sodium chloride is applied to ponds to control nitrite toxicity, stream or ground water salinization has not resulted from this practice; 9) fertilizers are applied two or three times annually to fry and fingerling ponds and occasionally to grow‐out ponds; 10) hydrated lime is applied occasionally at 50 to 100 kg/ha but this does not cause high pH in pond waters or effluents; 11) accumulated sediment removed from pond bottoms is used to repair embankments and not discarded outside ponds; 12) sampling above and below catfish pond outfalls on eight streams revealed few differences in stream water quality; 13) electricity used for pumping water and mechanical aeration is only 0.90 kW h/kg of production; 14) each metric ton of fish meal used in feeds yields about 10 tons of dressed catfish. Reduction in effluent volume through water reuse and effluent treatment in settling basins or wetlands does not appear feasible on most farms. However, some management practices are recommended for reducing the volume and improving the quality of channel catfish pond effluents.

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