I went n checked out the BiOrbs. Awesome looking fish bowls, but with some caveats that are not mentioned.
I can't imagine where they got their stocking numbers; 30 liters is less then 10g. Its strongly recommended just about everywhere EACH goldfish be given about 10g each, especially when they are over 2 inches each. Goldies produce a HUGE amount of waste as sweets said; that amount of water is needed to simply deal with the load. Those pics they show of 3/4/5/6 etc goldies in one of those tanks is horribly misleading.
The other issue I see with them is oxygenation. The bubbles which glide thru the water column do NOT add
O2 to the water; its the agitation of the water on the surface which promotes
O2/
CO2 exchange. The greater the surface area and the greater the agitation, the better the exchange. I see very little surface area in those tanks, plus I can't quite figure out how much air is getting TO the surface with that top. It looks to me they are more concerned with "coolness" then with the actual needs of the fish; shame really.
As for your poor goldie Fishygirl, I'm guessing his death was a combo of 2 things; ammonia poisoning and lack of oxygen. What happens is ammonia (which fish produce by digestion and respiration) burns the gills; the fish can't get enough oxygen. Combine that with the probable lowered oxygen levels in the tank and its a good bet he suffocated. I strongly suggest, if you haven't already, pick up an ammonia nitrite and nitrate tests so you can KNOW if there are waste poisons in your tank, and you can help your other fish be as healthy as possible by removing it. You may want to read up on the nitrogen cycle as its the KEY to a healthy tank; really nice article here all about it:
http://faq.thekrib.com/begin-cycling.html . Also, theres a great goldfish specific site on the net:
www.goldfishinfo.com