Table 2. Feeding and filter details for the three freshwater aquaria with controlled nitrogen budgets.

Aquarium code	Fish wet weight (g)	Biofilter volume (L)	Biofilter hydraulic residence time (s)	Upflow velocity (m/h)	Carrier material	Fish feed	Protein content (%)	Scenario 1 (days 0-21)		Scenario 2 (days 22-end)
								Feed dose (mg d−1)	Loading rate (mg N L−1 d−1) min - max	Feed dose (mg d−1)	Loading rate (mg N L−1 d−1) min - max
F4	239	15	56	27	t: fine sponge b:rough sponge	Tetra Cichlid flakes	48	200	0.3–0.73	1000	3.2–3.7
F5	190	5	36	9.6	t: sintered glass m: sponge b:ceramic rings	Tetra Goldfish flakes	42	200	1.6–1.9	500	4.1–4.8
F6 (temporal test)*	49	0.13	1.2	13	sponge	Vitakraft Vita Flake-Mix, Sera Viformo tablets	47, 45.7	80, 30	28–34	200, 40	84–103
F6 (spatial test)	49	6.1	31	19	t: fine sponge m:rough sponge b:ceramic rings	Vitakraft Vita Flake-Mix, Sera Viformo tablets	N.A.	NA	NA	NA	NA

Feeding doses were for cycles of five days on, two days off. The minimum biofilter loading rates are based on the measured nitrate production rates, while the maximum rates assume that all fed nitrogen is nitrified.

b, m, t: biofilter bottom, middle and top compartment, respectively. N.A.: not applicable.

* For F6 (temporal test), two different fish feed and their corresponding protein content and feed dose are shown by comma-separated text.