Ebb and flow versus constant water level on the sweet banana chili pepper (Capsicum annuum) production in an aquaponic system

Abstract

Bell siphons are used in aquaponic systems to create rising and falling water levels in plant culture beds that facilitates water exchanges and elevates dissolved oxygen (DO) although this may also remove nutrient rich organic debris from the plant culture bed. Sweet banana chili pepper (Capsicum annuum) plants were aquaponically grown until maturity and then further cultured in a media-filled bed with or without a bell siphon for one month in triplicate. Water quality was measured throughout as well as the total chili number, weight, mineral composition and sugar levels. Channel catfish (30 individuals/replicate; initial weight = 289 g ± 10.2) were fed twice/day for 5 days/week. Results showed that a bell siphon significantly increased DO in both the fish and plant culture tanks, but dissolved nitrogen and pH were similar. Fish growth, survival and feeding efficiency were similar among treatments. The total count (982 and 747) and weight of chilies (7450 and 7413 g) were similar without or with a bell siphon, but individually, chilies were significantly heavier with a bell siphon. Soluble and insoluble sugars were unaffected but among the tested minerals, sodium, potassium, calcium and zinc were significantly elevated in chilies cultured without a bell siphon. The lower mineral content was likely due to the bell siphon removing excess organic debris from the media-filled plant culture bed that would otherwise be mineralized. Based on these findings and under the culture conditions, bell siphons may not provide benefits to plant production and the lower DO may be mitigated by providing additional aeration in the plant culture bed.