Nitrate

[goose22]

Hi ive been having probs, since i bought my Fish pod 120 (120liter tank) it came with an internal filter, ive changed this for a fluvel 206 external filter.
added some new fish a cople of months ago,4x mollies 1x siamese fighter a few weeks later they died, went to Midenhead aquatics, they did water ters my Nitrate was 500! bright pink, they aske how often i did my filter clean/water chamge, Monthly as ive always done.
 
This is not correct? they said do a 50% change straight away, then i should be doing 25% every 2 weeks, ive done as they have said, the nitrate is lower but still not perfect, i am not adding any new fish yet!
 
i have 2 rosy barbs 2 silcer sharks, 8 neons 2 plecs & a cory, i have only plastic plants.
 
any ideas/sudjestions?

 

[TallTree01]

Well for starts your tank is way overstocked. The sharks, barbs and maybe the Pleco depending on the species will need a bigger tank.

Did you cycle the external filter?

If you want to lower the nitrate you'll need to do water changes weekly not monthly. Do it for a few days once a day so it lowers.

Live plants use nitrate to grow so getting plants will absorb some of the nitrate.

 

[goose22]

Over stocked its a 120 litre tank with 14 fish in it?

 

[fm1978]

It doesn't sound like you have given your filter time to cycle and not carrying out enough water changes while the cycle is in process.
 
We need to know more information to help you properly, too! What are the other water parameters? Ammonia, Nitrite, pH, temp etc? What kit are you using to test? How long have you cycled the tank for?
 
Right now, in order to control Nitrate levels you must perform regular and large water changes. 50% / day (or more in volume) for as long as it takes for those nitrates to get to as close to 0 as possible. I believe 20ppm is an acceptable level. Ammonia should be 0ppm as should Nitrite.
 
Live plants will also help with the reduction of Nitrates.

Over stocked its a 120 litre tank with 14 fish in it?

 
It's a bit more complicated than simply the number of fish in a tank of a particular size...
 
If you mean Silver Sharks, then they will grow to over a foot long and are just not suitable for that tank at all.

 

[TallTree01]

Over stocked its a 120 litre tank with 14 fish in it?

The fish species are the problem.
The silver sharks will grow to a foot or more.
The barbs will grow to 6 inches or more.
Both these fish need a bigger tank with a bigger group than your tank can give.

Do you know what species your Pleco is?

 

[the_lock_man]

Over stocked its a 120 litre tank with 14 fish in it?

 
It's not about numbers of fish, it's about the size of fish. You wouldn't, indeed couldn't, put a beluga sturgeon in your tank either - but that would only be 1 fish.
 
Silver sharks should grow to be around a foot long. They should be in a tank at least 6' long. You might argue that they are only little at the moment, but you should always take the adult size as your reference, if you keep them in a 120l tank, they will become stunted, and live a foreshortened and painful life.
 
You haven't said what type of plecs you have. Some stay very small, and would be suitable for your tank. Others reach 2 feet long. Again, if you have these, and keep them in your tank, they will become stunted.
 
So, sorry, but yes, you very much are overstocked.
 
Anyway, to move onto your actual query - the nitrate. Since you are seeing significant nitrate levels, it is clear that your filter is processing ammonia and nitrite, so your filter is cycled. There are two reasons why you are seeing such high nitrate levels. The first is the overstocking issue. The fish are producing lots of ammonia, which is in turn producing an awful lot of nitrate. The second is the maintenance. I would say you need to be doing 40-50% weekly. I would also suggest you buy a decent nitrate test kit, I recommend the Salifert one, which you should be able to get from MA.
 
As others have said, adding live plants will help. My tap water runs at around 40ppm nitrate (or it did when I last bothered to test it, which was about 2 years ago), yet my tanks run at around 5-10ppm. You should aim really, for no more than 20ppm above your tap water level.

 

[levahe]

Also keeping the substrate clean with a gravel vac once a week at the same time as your water change will help - a build up of excess fish waste and uneaten food won't do any good