Fish Dying Off - Possibly Nitrates

[scrufts]

Tank size:
pH: 6.4
ammonia:
nitrite: 1 mg/l
nitrate: 250 mg/l
kH: 3
gH: under 6
tank temp: 82 f

Fish Symptoms (include full description including lesion, color, location, fish behavior):

Volume and Frequency of water changes: 1/3 monthly

Chemical Additives or Media in your tank: gravel, bogwood

Tank inhabitants:2 plecs, 3 corydoras, 4 lemon tetra, 4 platies, 2 swordfish, 1 kribensis, 1 ram

Recent additions to your tank (living or decoration): swordfish, pearl gourami

Exposure to chemicals: nil

tank age: 7 months

tank size : 166 litres (138 x 38 x32)


Symptons: We have introduced the gourami and the swordfish within the last three months and have lost three swordfish and a pearl gourami - no spots or visible marks on body, just found them dead in the mornings when the light has switched on ( four deaths in a month), Changed half the water last weds. Tested today with above results - presumably the nitrate level is to blame as the long term inmates have not died - only the new stock.- the local pet shop have given me "bacterlife" which I have put in the tank a moment ago. mad with myself for not testing earlier and would like to know if there is any other way apart from water changes to keep nitrate level down if indeed this is the problem?
( I also have a three foot tank with a baby oscar and upside down catfish with same test results)

 

[WILDER]

How long has the tank been set up.
How many gallons or litres is the tank.
The reason for your bad stats if been set up a while is that you should be doing a weekly gravel vac and water change.
Plec are big waste producers, get the vac out and do a good gravel vac sound like this is your problem.
So small water changes as don't want to alter them stats to fast as it will shock the fish.
What filter are you using.

 

[scrufts]

Hi,
As mentioned in the post, tank is 166 litres and has been running for 7 months.
The filter is a fluval power filter and the foam insert is rinsed monthly. The water is also aerated via a long airstone at the other end of the tank.

 

[WILDER]

Sorry missed tank size.
I would still do the gravel vac, you are not maintaining the tank to well, debris and waste is building up in the substrate which can cause fish to become ill.
You need to be doing a vac and water change once a week.
Check your tap nitrates leave it a full 24 hours for a true reading.

 

[Griz]

While Nitrate is not normally considered to be toxic to fish, a level of 250ppm is very high and I have to wonder if long term damage might be possible at such high a level. My kit only reads up to 160! Regular vacuuming and water changes (daily, and likey for several days) will be needed to bring that level down under the 40ppm you want. Ideally you want less than 20. You have some work to do. Best of luck!

 

[KingKenny]

Why are your water changes so infrequent though? You should be doing your best to keep it far and away below 250. You should be changing at least 25% a week in reality. Mine is 30-40% weekly and the fish do well with that.

 

[BBrain]

I would be more concerned with your high NITRITE level, than your NITRATE level. Nitrite is many, many times more toxic than nitrate. Some fish are especially sensitive, and that might be what's actually killing them. I'm not sure if 1 ppm is toxic, but there should be zero.

What size are your plecos?

I had a single 3" pleco that had me vacuuming poop at least twice a day.

By "swordfish", do you mean swordtail?

 

[scrufts]

My apologies - I mean swordtails not swordfish.
My largest plec is approx 7" and he does leave a lot of poo!
Our current vacum cleaner is useless - it will only suck up the smallest bits of flake - what vacuum cleaners would people recommend?

 

[WILDER]

The hands ones are the best.

 

[MHunt]

A Dyson

Sorry, i just use a syphon but have the bucket well below the tank to get as much syphoning action as possible. I can't remember what make my vacuum is sorry, but it is quite effective.