Are My Fish Suffocating?

[BruceJW]

Hi folks.

New to the forum and the hobby in general.

I have recently set up a 46L Fluval Edge. I did a fishless cycle, regularly monitoring chemical levels, etc. First of all, I know this is a very controversial tank and there are many negative opinions about it.

After almost 2 months, I had 4 Black Phantom Tetras, 4 Red Crystal Shrimps and 3 Tiger Snails. I also have 3 moss balls.

All was going well and the fish and snails were thriving. I hadn't yet filled the tank to the recommended 5mm into the "neck" as I was waiting until I had it fully stocked. At this point, there were plenty little bubbles in the tank.

I added my shrimps on Saturday and decided to fill the tank with water. On Sunday there were less bubbles but I just put this down to the smaller distance the water now had to drop from the filter and thought nothing of it.

I fed all the critters before I went to work this morning and all seemed well. But I came home tonight and and everyone had migrated to the neck of the tank. Including the shrimp and snails! Three of the Tetras seemed to be gasping for air at the small surface and one had unfortunately died. So, I immediately removed some of the water and now the force from the filter is creating lots of bubbles again and everyone seems much happier after a few hours.

Do you think they were suffocating due to a lack of oxygen? If so, is this not a massive design flaw? Of all the stories I read prior to buying the tank, I never read anything like this!

Thanks in advance for any advice.

Bruce

 

[Donya]

Gasping at the open area suggests an O2 problem. However, that may not be what killed the fish. It could just as easily be that the fish died first, and dead animals can sometimes foul the water and cause O2 problems when there isn't enough gas exchange. Edge tanks have a much smaller area for that when filled than most tanks do. There are actually quite a few complaints about this sort of issue cropping up with edge tanks dotted around the web. Many keep them with no trouble, and then there are cases like this. It has always seemed like a risky design to me. If you don't mind keeping the water level low enough to have the extra surface area, then it would be safer to just keep it that way. 

 

[BerryAttack]

where the filter is, do you think there is space enough it put a bubblier tube. it can add oxygen to the tank, and leave your water levels up. i have not kept this tank, so i can't give a proper solution, but if there is room for a bubblier, you can play around and see if it works. if it makes no sense then never mind lol
oh, but if you convert it to a live planted tank it'll give oxygen

 

[BruceJW]

Thank you very much, ladies!

Everyone seems so much happier today and they're all acting normally again. The water force seems to be doing the trick.

I do believe that it was the lack of O2 that killed the tetra. Seems a bit coincidental otherwise. Also, would a dead fish affect the O2 levels that quickly? He was fine before I left for work in the morning.

If I did want to fill it again could I use an air stone or something similar to help with oxygenation?

Also, I did have live plants but removed them as it felt as though I spent most of my time removing their debris. Should I add more moss balls?