Actual sizes (and why a belly)

[EJA0000]

I often find it hard to know the length which a fish can become. Some species are given a length which is possibly a length which it gets in an average aquarium. So smaller then what it could become. Others are given max lengths measured in nature which you will hardly meet in captivity.

Unfortunately the species which I like remain either too small or become too large. I prefer to gamble on choosing the small ones with the possibility that it can become larger so I looked for three species to make a decision. I want a group of five (5) in the size 20-30cm.

I consider three (very common) fish species in the following order. I will only go and keep one of these species. Advice / experience would be highly appreciated and I will consider this in my decision.

1) L 168 Zonancistrus / Dekeyseria brachyurus
Normally this specie max out on 14 cm. Is there a possibility if I place them in a 500 liter aquarium of 180cm (L) x 80 cm (W) x 45cm (H) that they will grow larger in time to about 20cm?
2) Pimelodus pictus
Normally grow up to 13-15cm. Is it possible that these will grow larger to also atleast 20cm?
3) Platydoras Armatulus normally they say they grow to 20 cm but I know they grow up to be larger. Which is perfect for me. I absolutely love the way juveniles look. The questions I have in regards to this specie:
- In most aquaria they get quite a big belly which I don’t like. Multiple pictures of the specie in nature do not show this belly. Aldo the answer seems obvious I still like to ask it, "Why do they get this belly and is it possible to prevent this in an aquarium"?
- Juveniles can have bright white stripes. Adults often show a more light brown stripe.
I know the Armaturus and the Costatus often get confused and the pictures on the internet are not always in line. Question I have is can the white stripe remain white as an adult or will this color become more light brown?

Many thanks in advance,
EJA

[Jools]

Good questions.

Max. lengths measured in nature are a minimum, the only reason a fish kept in captivity doesn't attain these is keeper error. In most cases, they are also convervative, but it depends on the sample size - typically low.

Sizes are SL not TL (look up the glossary).

1) Not likely.
2) Likely.
3) It's in the FAQ, but basically they pig out. Feed them regularly on small amounts and you won't get the fat belly. As to colour, it depends on the catch locality but generally they will dull as they age. The fish in the trade is

Platydoras armatulus

which was long misidentified as the other species.

Jools

[Bas Pels]

@3, size of Platydoras, I got 2 which must be over 30 years of age now, I bought them in 1988 @ 7 cm, which are 20 cm and not more.

As this species does have a large distribution area, chances are other populations might grow bigger, but you don't know what you get. I'd assume you get the regular, which grows to 20 cm

[EJA0000]

Jools and Bas, thanks for your answers!
30 years is a very long time. Respect!

I understood most catfish are from the wild and not bread at farms. Does this mean that there is a possibility that I can ask a seller/trader for a cites paper, which should indicate the place of where they are caught?

[Jools]

No, it's more like knowledge of the supply chain. If you buy from great stores then they tend to know this, the chain stores don't know where the fishes come from specifically.

Jools