fishes Article Effects of Dissolved Potassium on Growth Performance, Body Composition, and Welfare of Juvenile African Catfish (Clarias gariepinus) Lisa Carolina Wenzel 1,*,†, Sebastian Marcus Strauch 1,*,† , Ep Eding 2, Francisco Xose Presas-Basalo 1,2, Berit Wasenitz 1 and Harry Wilhelm Palm 1 1 Professorship Aquaculture and Sea-Ranching, Faculty of Agricultural and Environmental Sciences, University of Rostock, Justus-von-Liebig-Weg 6, 18059 Rostock, Germany;
[email protected] (F.X.P.-B.);
[email protected] (B.W.);
[email protected] (H.W.P.) 2 Aquaculture & Fisheries, Wageningen University and Research, Droevendaalsesteeg 2, 6708 PB Wageningen, The Netherlands;
[email protected] * Correspondence:
[email protected] (L.C.W.);
[email protected] (S.M.S.) † These authors contributed equally to this study. Abstract: Optimal crop production in aquaponics is influenced by water pH and potassium concen- trations. The addition of potassium hydroxide (KOH) into the recirculating aquaculture system (RAS) may benefit aquaponics by increasing the water pH for better biofilter activity and supplementing K for better plant growth and quality. We investigated the growth, feed conversion, body composition and welfare indicators of juvenile African catfish (Clarias gariepinus) treated with four concentrations −1 Citation: Wenzel, L.C.; Strauch, S.M.; of K (K0 = 2, K200 = 218, K400 = 418, and K600 = 671 mg L ). While growth, feed conversion Eding, E.; Presas-Basalo, F.X.; and final body composition were unaffected, the feeding time and individual resting significantly Wasenitz, B.; Palm, H.W. Effects of increased with increasing K+. The swimming activity and agonistic behavior were reduced signifi- Dissolved Potassium on Growth cantly under increased concentrations of K+.