Never Put Water Melon In The Tank For Fish

[PolyVinalDistillate]

I know this is an old thread, but I came across it while checking up on the safety of watermelon. For others googling, I decided it was worth replying.

The OP describes a situation very similar to what happened to me when I placed a chunk of butternut squash in my tank overnight (research had suggested this would be fine). I happened to wake up earlier than usual that morning (luckily) and discovered a tank that had gone extremely cloudy. All the fish and the assassin snail were at the top of the tank due to depleated O2, and there were whispy strands attached to all the decorations in the tank. I lost quite a few fish over the following hours...

Research suggested I had experienced a bacterial bloom that had starved the tank of oxygen. The butternut had not dissolved into the tank, but I know it oozes after being cut, so my guess is that was enough to trigger the bloom. I turned my filter up to maximum and had it sprinkling on the water surface to aerate the tank as much as possible, as well as doing an emergency 30/40% water change. Over the course of a few days (and several filter cleans) the gunk in the tank cleared, and the fish I managed to rescue were mostly fine. I did lose a further Rummy to fungus afterwards, so I guess it was weakened by the oxygen starvation.

Having read that this can happen with melon (water or otherwise), I think I'll be removing the piece I just put in the tank in the next hour or two after the Guppies and Otocinclus have had a bit more time to enjoy it. It was swarmed the moment I put it in, so I'd feel a little bad removing it so soon!

The tank is only ~30 litres, so perhaps butternut is safer in a bigger tank? But I know I won't be putting butternut in again, and I'll be sparing with the melon having read this.

 

[Magnum Man]

I honestly think the key here, is the size of the piece, if for example, you calculated the volume of the pieces of melon, ( or squash for that matter ), and placed that volume of fish food in the tank, I’m betting you would see similar results… we just don’t typically put that much fish food into a tank, weather that’s pellets, Mellon, or squash, even a thin slice of cucumber, by volume, is a lot… more, is often not better…

 

[Colin_T]

Never leave uneaten food in an aquarium for more than 15-30 minutes. The only exception to this is small amounts of thinly sliced fruit or vegetables that can be left a little longer (up to an hour) if the fish are eating it. However, if nobody is eating it, remove it so it doesn't rot and create an ammonia problem.

All tanks need aeration/ surface turbulence and most power filters need their outlet above the water surface to make any difference to the oxygen level in the water. An air pump and airstone is the best way to increase aeration in water.

If you ever have an issue like this (poisoning or possible lack of oxygen), do a massive (75-90%) water change and gravel clean the substrate, and increase aeration.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.