High Nitrates Low Everything Else!?

[tha pint]

I've a rio 240 with a fluval 405 with a fully grown oscar and a breeding pair of severums. The tank has been going for about a year but over this last 2 months I've had a bad dose of brown Albee diatoms or whatever they are called . Also had a high ammonia problem at Christmas but back then I had 2 catfish but I rehomed them to cut down on the bio load. Every week I do aprox 40% Wc and only just done one yesterday after I had hoovered all the sand out of the tank to leave it a bare bottom as it was clogging the filter and upsetting the severums spawning. I've a load of bog wood in it for the oscar to prowl over and a clay flower pot for the sevs.

Tested with API master test kit today.
Ph 7.5
Ammonia 0
Nitrite 0
Nitrate between 80/160 !!!.

Why is my nitrate so high after the change yesterday. I added more porous media rock stuff to the 2 spare parts in the filter today. Maybe not enough bacteria?

I'm not sure what's going on. Btw green algea seems to love my tank ATM.

Hope that's enough info

 

[Shelster]

Have you ever checked the parameters of your tap water?

 

[Skry]

I can imagine algae would love your tank with that high a nitrate level.
 
Nitrate is the end-product of the nitrogen cycle for your tank.  It will stay in the water until it is removed through water changes, consumed by plants (like algae), or handled with some form of chemical or highly-specialized biological filtration (read: expensive).  It requires a huge amount of plant life to handle the nitrate production caused by a very few fish (and you'd still need water changes to mitigate buildup of different trace elements/minerals).
 
If your rate of nitrate removal is less then the rate of nitrate production from the ammonia sources, then you will get a buildup.
 
Fish Herder also has a very good point.  If you live near or down-stream from a farming community, nitrates from the fertilizers can get into your tap water.  Using RO water for some water changes might help mitigate that.
 
EDIT:
Just to clarify, the bacteria in your tank are definitely doing their job.  The only bacteria that break down nitrates and release nitrogen gas operate in an anaerobic environment, which is generally hazardous to your aquarium as it can also breed other toxic bacteria.

 

[star4]

The tank is overstocked still, your going to need to do a wc twice a week or get a bigger tank

 

[tha pint]

Ive allowed the back pane of the tank to get covered in Algae as I assume this will use the nitrate . Should I maybe add another fish ? I'd fancied a red parrot but was afraid to overstock as I thought I was pushing it already .

I'll test my tab water tomorrow but I think its ok as I've ran tanks for a few years an never had blooms like this.

The tank is overstocked still, your going to need to do a wc twice a week or get a bigger tank

yeah I'd thought that as I know it's just about big enough for the oscar.

I.ll double the wc and see what happens.

 

[tha pint]

Ok the next day I done another 50% wc and it halved the nitrate level . Algae has started to go a bit and the water looks nice and clear. Tested my tap water and it came up 0 for nitrates.so I know its not that. I assume without plants unless a do heavy wc's twice a week or more this problem won't rectify . If I do decide to plant what plants could I use with an oscar and severums . I know they are notorious for tearing plants to bits.

 

[fm1978]

When you make a change and then something weird happens right after the change, it's usually the simplest explanation that's the right one.
 
In your case you may have released into the water loads of trapped Nitrate during the hoovering up all your sand. So, after a few more water changes it'll go back to normal and it'll be a happy tank again... 

 

[star4]

You can sometimes get away with anubias or java fern with oscars and severums, I have never managed it mind lol but I have seen some other pictures of tanks with oscars and severums with plants. The only thing to do is try it and see. Personally I would go for a bigger tank

 

[tha pint]

When you make a change and then something weird happens right after the change, it's usually the simplest explanation that's the right one.
 
In your case you may have released into the water loads of trapped Nitrate during the hoovering up all your sand. So, after a few more water changes it'll go back to normal and it'll be a happy tank again...

That would make perfect sense as when I hoovered up there was pockets of gas underneath rocks and stuff. I'm gonna hit it with another 50% then start 25s for the next 2 weeks.

You can sometimes get away with anubias or java fern with oscars and severums, I have never managed it mind lol but I have seen some other pictures of tanks with oscars and severums with plants. The only thing to do is try it and see. Personally I would go for a bigger tank

My oscar is a bit of bugger and kinda has a go at most things ie the heater and hands so I don't know. I had a load of marimo moss balls in another tank a while ago and they seems to keep the green down. As far as a bigger tank goes ATM I can't because my 240 sits on a spot where a fire place used to be and it's the only solid floor in my living room. My house is over 100 years old so I wouldn't feel safe putting a serious weight like a 6ft tank on the joists. the chimney breast is exactly 6ft but the hearth is about 4ft which seems to be block to the ground . That's what I set the tank on. I'd love to go bigger like a 6ft.

 

[Ciddire]

Ok the next day I done another 50% wc and it halved the nitrate level . Algae has started to go a bit and the water looks nice and clear. Tested my tap water and it came up 0 for nitrates.so I know its not that. I assume without plants unless a do heavy wc's twice a week or more this problem won't rectify . If I do decide to plant what plants could I use with an oscar and severums . I know they are notorious for tearing plants to bits.

 
The only plant my sev (george) goes after is Pennywort. He'll shred it with a vengeance. I don't actually mind because I'm not a huge fan of the stuff anyways.
 
I've got a heavily planted tank and besides a few nibbles here and there I don't have any trouble. 
 
If you've got any friends with planted tanks see if they can give you some clippings and see how they do.
 
Worse case scenario your fish got some green in their diet and some amusement. lol