Research Paper to Read: (2018) Minimal water volume for intensively producing male Siamese fighting fish (Betta splendens Regan, 1910)

Source: Research Gate.

Takeaways
(1) 150 mL water volume within 2 - 9 cm depth should be the minimum and optimum water volume to rear individual male Siamese fighting fish.
(2) Jar the fish when it reaches 1.5 months old (6 weeks) and sell it at 4 months old (16 weeks).

Why this paper?
Betta fish (B. splendens) is an aggressive and territorial tropical fish. To defend its territories, a Betta fish will flare its gill and spread its fins. Furthermore, it will bite its intruder. Therefore, upon reaching adulthood, the male Betta will need to be separated and jarred into separate and smaller container. However, a Betta fish spawn, on average, contains few hundreds of fries. Hence, to fully utilize available spaces and giving the Betta fish the optimum growing environment, what is the minimum water volume or container size that can achieve this? Our observation is most breeders will use several cost saving ways to jar individual male Betta fish. These consists of using recycle mineral water bottle, thin glass alcohol bottle, or drinking plastic bags.

Material and Methods
This is a randomized design experiment of 5 water treatments and 15 replicates. First, one-month old solid-red male Siamese fighting fishes were purchased and individually acclimatized in cylindrical plastic breakers (7.5cm diameter x 12.5cm height) of water volume of 250mL for 2 weeks (not sure why?). Then, 15 fishes (n = 15) of similar size (0.97 ± 0.01 g initial body weight)were evenly and individually distributed into 5 water volumes of 100, 150, 200, 250, and 300 mL glass aquaria (3.5cm width x 8cm length x 20cm height).

Breeding conditions for 8 weeks or 2 months as follows:
(1) Commercial floating pellets (10% moisture,  46% crude protein, 6% crude lipid, 5% crude,
fiber, and 12% crude ash).
(2) Feeding done twice daily (08:00h and 17:00h) at 2% of body weight.
(3) Photoperiod of 12h (light) : 12h (dark)
(4) Uneaten excess diet were siphoned after 30 minutes after feeding.
(5) 80% water changes with dechlorinated stock water within 3 consecutive days.

Since it's too long and quite complicated (I don't really understand it), I skipped the part on what measurements and tools used.

Results
Only the results for water quality and overall growth were discussed here.

Since leftover food were siphoned, the only contributing factor to water quality is the ammonia level due to excreted water by the fish. The lower the water volume, the higher concentration of ammonia level and lower pH level as shown in table below for water volume of 100mL.


Large water volume (300 mL) will lead to bigger fish growth (standard length) and at the same time, allows more space for increase movement (like bubble nest making) within the container, and thus, low weight gain.


Discussion
How big is 150mL? The video below will give you some idea. Should you use this minimum water volume for optimum growth? Depends. If you have large quantity of fishes, limited spaces, and plenty of time for water changes, then this should be the right option. If not, use the largest water volume possible so less than frequent water changes. When breeding and rearing Betta fishes, water changes is the only task that consumes most of your time.



Further Questions
(1) Will plastic bottle instead of glass aquaria have any significant effects on the experiment?
(2) When do we start to jar the male Betta fish? Is it 1.5 month of age when it starts to show aggression behaviour or when it reaches certain size of 2.5cm?
(3) Will there any significant changes if the water were treated with Indian Almond leaves?
(4) Is there any significant impact to the result if these fishes were fed with live food sources?
(5) Large water volume means less frequent water change. Is there any impacts on frequency of water change to the result?

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