Problem In The Big Tank, Any Ideas?

[Spishkey]

i seem to have a problem in my big tank (500L community)
ive lost four fish over the weekend and am totally stumped as to what the problem could be?

ammonia 0, nitrite 0 nitrate 20

first to die was my angel i found him stuck in the filter and he died the following morning, no sign of infection just marks from being stuck. on the same day i found a dead platy (hardly recognisable mostly eaten) then that evening a cory was lying on his back, an hour later it was dead. then yesterday my largest pleco was dead again no visible signs of any infection or parasites. no redness, no swelling or inflamation. no fish flicking or itching, no gasping, nothing new added to tank.
im scared something is working its way through the tank and im gonna loose more fish or the tank is crashing??
its been set up since last year, always been a very stable healthy tank.

any ideas to what the problem could be people?

 

[Marclau]

Sounds a bit similar to what I just been through past week.............

Not to scare you but in the end, I lost over 50 fish.......

Any signs of redness or long worm like poo coming from the fish.......this could be signs something is wrong.
Any slime also??

I would do a 30% water change in any case..........not sure..........

 

[Spishkey]

did water change on saturday evening, cant see the point in doing another now?
poo's all look normal (from the fish ive seen poo!) i cant figure out what i t could be?? no symptoms no signs just death. the only one we saw show any sort of sign it was ill was the cory who was fine all day, then was lying on its back then dead.

 

[Marclau]

Honestly, I would still recommend water changes.........I did it for my tank for the past 4 days...........finally getting stable and no more deaths.......I lost around 50 fish......
Only 2 Gouramis left.........

I took the advise of Miss Wiggle and others and they all recommended water changes...........

Whats the temp of the water currently? Also have you tested for Ph?? If so,what are the readings?

 

[Spishkey]

temp is around 25. no idea of ph have never tested for it! will test it in a moment

 

[Marclau]

Ph is the measure of the water acid and alkaline conditioning of the water...........most a special nutrient salt based added to the water each time you add water.........
Ph levels can effect fish although not as drastic as say Nitrite or ammonia. It also depends on your fish type.

If Ph drops below 6, carry out a water change. pH is a measure of how acid or alkaline water is, and is held stable by minerals dissolved in your water. A stable pH is more important than one in the ideal range, unless your pH repeatedly drops below 6. If the pH repeatedly drops, you are short of minerals in your tap water. You can add coral sand or coral gravel to the filter or substrate to up the hardness of your water, and raise the pH. This will hold the pH stable at this new value, unlike many other chemicals. Make sure you add this slowly, until the pH reaches 7. Adding too fast will stress your fish. (thanks to Miss Wiggle in earlier post long time ago)

 

[Spishkey]

sorry that sentance made no sense to me whatsoever

 

[Marclau]

Post your Ph level on here and we can advice if this is within range..........

 

[Spishkey]

ph is 7.4

 

[Marclau]

Damn, seems alright and within limit............usually around 7.0 - 7.4 is good range.

You may need to have a fish biopsied to help identify cause.........some good LFS should be able to do this (and for free)....mine does....ummmm

 

[Davo86]

Whats the temperature?
if all stats are fine then it could be due to lack of O2 or a chemical has somehow entered the water (deodrant, air freshner or similar)

To be on the safe side I would be doing a 50% water change asap. In most cases, regardless of the problem, this will help with things.

 

[Marclau]

temp was already mentioned at 25 degrees.............agree about water changes..........

 

[Spishkey]

lack of oxygen is not the problem, i have a spray bar angled into the tank which sprays bubbles mixed with the water half way across and all the way down the tank
its a closed tank so nothing could have settled on the surface. 50% water change is impossible on my own(250L with just a 20L bucket!), have just managed about 60 litres though.

no deaths (so far) today. all other fish look fine and dandy. what else could it be? just a coincidence?

 

[craig855s]

you got black carbon in your filter? Any automatic air fresheners anywhere in the room? Id do a couple more water changes over the next few days so if there is anything in the tank it will soon be diluted to very low levels,and carbon will help remove it

 

[england]

sometime's you could be just unlucky, heating sound's ok all other stat's seem ok.....is everything working correctly on the filter and it's all connected corectly?
heater is ok as in not cracked or anything like that?
added anything new recently or new food's?