Green spotted pufferfish (tropical) with dark underbelly?

We purchased some pufferfish yesterday from our local aquatic centre. In terms of selecting the puffer fish we wanted we asked for a dark belly and a white belly.... Only to get home and realise that the dark belly meant he(?) was stressed out. The other puffer has a white belly and has throughout. We were just wondering why his underbelly remains darker and if this means something is wrong with him... It has been this colour since we saw him at the aquatic centre.

Also wanted to work out if we have male/females.... any idea how we can work this out?

Hi and welcome to the forum

Can you post some pictures of the fish so we can see them?

Colin_T said:

Hi and welcome to the forum

Can you post some pictures of the fish so we can see them?

Click to expand...

Hi Colin!

Many thanks Have attached some images (there are multiple images, one of which has the white underbelly and the other has the dark)

Thanks for responding and look forward to hearing back!

The light one looks happy and healthy. The darker one is really stressed out.

Make sure the pH is above 7.0 and add some salt. You can use rock salt (aquarium salt or swimming pool salt) or sea salt in the tank. You want the water about half strength sea water.

The stress could be from bullying by the other fish or it could be from shipping or water chemistry (pH, GH, KH and salinity).

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I can't help with sexing them.

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Did you cycle the tank before adding the fish?
Cycling the tank is where you let the beneficial filter bacteria develop over a month or so and then add the fish once it has developed.

If the tank has not been cycled, then reduce feeding to once every couple of days and do a 75% water change and gravel clean the substrate 4-8 hours after feeding. This will help keep the ammonia and nitrite levels low while the filters develop. Once the filters have developed, you can feed more often and do a 75% water change and gravel clean the substrate once a week.
Make sure any new tap water is free of chlorine/ chloramine before it's added to the tank.

If you are adding salt (these fish come from brackish/ salty water), add the salt to the new water and let it dissolve before adding the water to the tank. This will keep the salinity (salt level) in the tank stable.

this seems like an impulse buy.
based on the picture, the tank is FAR too small even for the smallest of puffers.
i consider puffer care to be very intensive compared to other fish, ESPECIALLY the green spotted due to salinity requirements.

there are three most important things when owning a puffer long-term:
1. you must feed them (expensive) hard-shelled foods, or they will die (due to their ever-growing teeth).
2. you must keep them in adequate housing. their bio-load is very high and for two GSPs, in an aquarium smaller than about 40 gallons, even with increased water changes, they will suffer greatly.
3. never try to keep puffers in pairs, they WILL kill each other.
also, if the tank is not cycled, they will very likely die, or be permanently scarred.

if you're set on keeping pufferfish, i suggest returning these and starting with an easier, freshwater species (a group of dwarf puffers would be better for your tank size).
yes, pufferfish are very cool, but it's very uncool to mistreat them - they're not toys.