Nitrate Woes

My nitrates are always over 80ppm, they are now and have been for the last twelve years, since I moved here; I gave up worrying about it as I lose no fish and everyone is in fine fettle. I do two 200 litre water changes every week and don't even bother checking nitrate levels anymore as I know they'll be high.

Good to know thank you mate

Well, plants need CO2, light and nutritients, and o2 at night. How they get that is not relevant. But of course some of them would grow better with their roots planted into some sort of medium which isn't too big to prevent the roots from spreading.
In terms of nitrAtes many species don't care about the level. What matters is that before it becomes nitrAte it's been in the form of organics first(bad in itself), then toxic ammonia then nitrIte, then finally nitrAte.  All these processes need lots and lots of oxygen as well which affects the enviroment.   So having high nitrAtes is not a problem in itself, but the question is why.  And that's presuming your nitrAte test is accurate which often isn't.
The best way to deal with that is to either target the organics via siphoning the substrate/cleaning the filters, feeding less, reduce stock, do more water changes, etc..or..A possible chemical approach is purchasing Seachem purigen which removes organics from the water directly preventing them from becoming anything else than that.
However, as already mentioned by other members, having lots and lots of plants that can utilize that ammonia before it starts converting to other forms is the most pleasing way and the fish would prefer such an enviroment. But it's not cheap or easy to have healthy and fast growing plants with little effort. 
 
An alternative to aquatic plants would be emersed plants as they can draw CO2 directly from air and thus as ammonia/nitrite/nitrate removers are even more efficient than aquatic plants.   I have some peace lilies, calatheas, etc..growing with their roots only in water planted in hydroton pebbles in planters like in the picture below. This may require modification of the hood or converting to open top aquarium but once done and the plants adapt, they start really appreciating the waste fish produce and there's no need to worry about CO2 ever.
 
Here are some of mine:
 

 

 

I'm still having worries with my Nitrate levels. 
 
Since I last posted, I have added another 8 moss balls so have about 10 now which have all grown. I am not prepared to buy any other plants apart from these as they just get attacked or just die too quickly.
 
I am still doing 80-90% water changes every week. My filter contains:
 
Ceramic media
bio balls
fine sponge
coarse sponge
Seachem De-Nitrate
Filter floss
 
I'm going to order a couple of Seachem Purigen pouches as I don't know what else to do now really. I run them in my marine external filter with good results so we'll see.

Oh and the reason I want to get the level down is because I know that my fishes general health will deteriorate although not necessarily noticeably. Also, if I were to add any new fish the shock of a higher nitrate level would probably kill it.

I got 10+ Cryptocoyne Wendtii, and about the same number of Vallisneria, about a week ago. Fertilizing once a week with 10 squeezes of Tropica Premium. Well, now I have a well planted tank... with diatoms growing all over the leafs! The attack on the walls has somehow ceased, for some reason.
I guess it needs time for the plants to adapt and start up again, but for sure now it's impossible to clean the bottom and the plants leafs, without uprooting them...

Diatoms on plant leaves in an established aquarium can only mean one thing, - the light intensity is too high.

Thanks levahe,
well, I have the standard 2xT8 38 W that came with the tank two years ago. Water level is pretty low, though (150 rather than then available 240 l), so I guess absorption is quite reduced. I have a bunch of mangroves slowly growing in there, which of course do need good lighting. I may try to shade a bit, but how will this affect the plants??
 

You could try floating plants to provide shade to the underwater plants while maintaining the higher lighting for the mangroves?

I use 2x 30w T8s in a 160l (100x40x40cm) and the lighting causes diatoms to grow, and other types of algae as well. the only way i have managed to stop this happening is by decreasing the lighting intensity, or by using pressurised co2 and high levels of fertilisers

If your lighting level is very bright, you need to match this with high levels of co2 and fertilisers. Your tank is low tech (no added co2)
So you need to have a lower light intensity in order to have a algae free aquarium. There is no way to avoid the algae other than reducing the light brightness.

A lot of people assume that they need to provide more light to make their plants healthy, but really what they need is less light or more fertilisers and co2.

Actually diatoms are the result of a couple of things, one of which is often too little light rather than too much.
 
Have a read here: http/www.aquascapingworld.com/algaepedia/full_view_algae.php?item_id=79

 
[SIZE=small]Adjusting Photoperiod[/SIZE]
[SIZE=small]Brown Diatom algae do well in low light conditions.  Increasing the photoperiod gradually will prevent the diatoms from taking a foothold in your aquarium.   Do not exceed 10-12 hours a day as these conditions will favor diatoms as well.[/SIZE]

Click to expand...

 
Exceeding 10-12 hours will also make you a lot of algae

There is a lot of false (old out of date) info in that article, it claims that its also caused by phosphates *false* and silicates *false* nitrates *false*
This type of algae has been found to be only caused by too much light.

Thanks both.
 
I have encountered quite often these two schools of thinking about diatoms: someone says they thrive in low lighting, someone states exactly the opposite. My experience is clear: in my tank, they grow in the most exposed parts of the tank; shaded areas are less affected. I have already decreased long ago the photoperiod from 8 to 6 h, and I don't feel like going lower than this.
 
As a floater, I have tried Limnobium, which I liked a lot, but died quite soon.
 
One thing I haven't done in a long time is to give a couple of days of total lights off, just after a good clean up. But I'm pretty sure it will work only for those 48 hours...
 
Silicates: the relation with diatoms is stated in lots of places. Levahe, can you point me to some literature denying this? I never managed to find some silicate test, but having sand in my tank I always assumed to have them high, together with my damn 50-75 mg/l NO3, due to tap water.

I don't have any links to scientific papers to prove this but it is generally accepted by leading planted tank enthusiasts on aquatic plant specific forums, that diatoms are only caused by too much light.

That and my own experiences and trial and error. I only give advice about problems that I have personal experience of and have managed to solve using methods I found on the internet. Before I solved my own diatoms problem I tried all the advice found on the internet. The only thing that worked is less lighting intensity or to add enough co2/ferts to match the high lighting. I can induce diatoms then make them go away again.
You only have to try it yourself to see !

Many thanks levahe!
 
I will definitely take your advice, and go that way. I have indeed shielded my lights for a while time ago, to calm down my archers, so I can try the same agan, or better buy some lower intensity bulbs.
 
I have about 150 l in a 120x40x30. You mentioned in about the same tank you still diatoms with T8 30 W: should I go even lower than that?
 
Thanks!

You could try raising the lights if possible, or removing reflectors if there is any. Other things to consider are cover the light tubes with something like ladies tights or there is fluorescent light sleeves and diffusers available. Removing a bulb but there has to be a way to cover the exposed light contacts.
If you fancy treating yourself to something nice you could get some led lights with a controller to adjust the lighting brightness but that costs a lot of money

Indeed. Light is the clue. Thanks levahe. For the time being I simply set back the plexiglas cover where fake mangrove leafs hang from, and that has already had a visible effect.
Next step will probably be to raise up the whole lid & lights, since the mangroves will soon need more aerial space anyway.