Danio behaving weird

Question
Hi, I have 6 Danios in a fairly new tank (the tank is 130 gallons, approx 8weeks old)and I've had the fish approx 4 weeks and dispite one of the Danios really worrying me by getting himself stuck and injuring himself (which he seems to have recovered from now), in 4weeks I haven't had any problems. Over the last 5 days I have noticed that one of the Danios are swimming very differently to the rest, he seems to be diving irratically and especially diving towards the ground keeping his nose to the floor and standing vertical, he also speeds up randomly and also does not come to the top of the tank for feeding. I done a partial water 25% change 1 week ago and since I have noticed this behaviour but only with the one fish. I did not use any harsh material to clean the tank therefore I cannot understand what has happened he almost looks like he has a mental health problem or seems very anxious. I am a bit worried as he is still in the same tank with the others.

I have checked my water readings and they are as follows
GH - 180, KH- 120, PH -7.5/8, Nitrite - 0 & Nitrate 2 Water Temp 70-72. I am unsure how to check the ammonia level?

The breathing does seem faster than the other fish and there are no visible spots on the fish. On closer inspection I have noticed that the right fin is flapping faster than the left, which could be causing it to circle/whirl round and also the slow then rapid movement, it is also tilting to its right and is staying at the back on the bottom of the tank kind of leaning at times on the glass. It has totally isolated itself from the other 5 Danios.

I haven't done anything different than normal to the tank nor have I added anything new to the tank. I weekly use TetraAqua EasyBalance & King British Safe Water, and I also treat new water with TetraAqua AquaSafe, I do not usually do a partial water change as 'EasyBalance' is used so that water changes are not necessary for approx 3months (and also tank has only been running for 2months). Obviously every week I do my 5 checks and I also 'top up' any evaporated water its normally about 10litres and this is treated with the aquasafe and also filtered water. I feed the fish with TetraMin flakes and the use by date is the end of April '09.

I have tried to take a pic ture but he's hiding in the darkness of the back of the tank, I will keep trying tho.

Many Thanks,

Emma.

Answer
Hi Emma,
The poor little fish. I don't think its anything you have done wrong.

What it sounds like to me is a swim bladder problem or some other internal issue like perhaps even trauma to the brain/nervous system.

The former we can do something about. But unfortunately the latter there's not much you can do but hope that he can recover.

The Swim bladder is special organ that virtually all fish have and its job is to control the equilibrium and overall balance of the fish. If something interferes with it, the poor fish will loose almost total control of his swimming and cannot swim straight for long and some fish sink to the bottom or float uncontrollably at the surface against their will. They may also "nose-dive" where they try to swim but its like they have an extra weight pulling their nose down the whole time. Or there's an invisible string pulling their tail up towards the surface.

The main causes of swim bladder can be due to fish swallowing too much air when they eat at the surface, injury from other fish or the individual's own reckless behavior, or too much dry food and/or not enough variety. The food issue is because digestive problems like a blockage puts pressure on the swim bladder.

The condition can get better on its own. But sometimes if its diet-related than they need some help in the form of offering foods that help their digestive system get going again like mashed green peas or the perhaps tastier alternative-- frozen brine shrimp or daphnia.

Notice if the danio looks bloated or has trouble going to the bathroom which of course would signal that constipation issues are responsible for his swimming problems.

His little body may be shutting down from water problems or just a general 'weak fish'. I really find it hard to think there could be a water quality issue being that the tank is so large and there are only a few fish in it. But testing for ammonia is always important regardless. You can test for it just as you do the other water levels with  simple test kit from your petshop.

I think the best thing we can do for the danio at this point is try our best to help him out as if he has a swim bladder issue. Offer frozen brine shrimp (maybe try to find baby brine shrimp frozen) or daphnia and notice how his belly looks (if its bigger than the others)  and if he is willing to eat at all.

Best of luck and let me know how it goes.
The little guy may not make it, it sounds like he is having a really rough time. :(

Karen~