Have I enough oxygen?

[WeeMan]

Hi my best mate bought me a 30L tank for me b'day 2 months ago and all is well except for recently some of the fish are swimming to the top, gasping for air. Having searched various sites I have been instructed to replace 80% of the water, clean out the filter and clean th gravel. All this has been done, I think that this has happened due to me overfeeding However even now a couple are still "gasping". I have 2 blue tail tetras im my tanks and these are the "gasping pair", two swordtails "occasional gaspers", 3 red eye tetra "very occasional gaspers", two six stripe tiger barbs "very occasional gaspers" and one black synodontis cat fish "never gasps". I have done pH tests, Ammonia tests, Nitrite and Nitrate tests and all are fine. I have all natural plants and so I am wondering if I need an air pump?

 

[clutterydrawer]

could you tell me the length and breadth of the tank? It sounds very, very overstocked.

 

[WeeMan]

Hi, my tank is 40cm long by 20cm deep by 30cm tall, this is slightly misleading however as it does not have a flat front more of a hexagonal look. My local fish stockist said a maximum of 12 fish for this tank however I am more than open to any other ideas.

 

[clutterydrawer]

He said 12 fish without saying what kind of fish? Would he think 12 great white sharks could live in there just as well as twelve tetras?

Anyway. Your tank is 8 gallons and probably has the surface area to support about 12-14" of smallish (tetra-sized) fish. I don't know what kind of synodontis you have, but even ignoring it I count 20" of adult fish, more if you take into account the fact that swordtails and tiger barbs are big for their length (they are broader and deeper than tetras).

Basically I don't know how big they are currently but as your other readings are fine I do think you've got a problem with oxygen in the water. An airstone will help at least temporarily but I think it might be necessary to look at rehousing some of the fish, either by returning them to the shop or by getting a bigger tank. sorry mate

If you want to be absolutely certain of the cause you could try getting a test kit for oxygen - I didn't know such things existed but I saw one the other day. Might be worth a try.

 

[WeeMan]

Thanks I guess this was a bi of beginner stupidity! But I do feel Ive had some duff advice, anyway Im going to get an airstone and then remove some of the larger species.

 

[clutterydrawer]

It's ok, most people get shoddy advice when they start off and it's almost always on the part of the fish-shop-staff.

In future, a good formular for stockingg a tank is to calculate the surface area and divide by 30 to give the length of fish in cm that the tank can support. Again applying to smallish fish like tetras and danios, bigger fish need a bit more.

happy fishkeeping