Dosing Nitrates

[Waterloo Kid]

I thought I'd start a thread about my experiences with dosing nitrates.

My tank has always had a problem with blue green algae (BGA) and my nitrates have always been low. It has been stated that BGA can result from a nitrate limited system (a tank environment in which nitrates are the limiting factor in plant growth) or an excess in phosphates. My phosphate reading is relatively high at approx .75 - .5mg/l.
I decided that dosing nitrates would be a good semi-natural way of combating this annoying and ugly algae.
I bought 500 grammes of POTASSIUM NITRATE (KNO3) from www.gardenchemicals.co.uk. Probably not the cheapest place but I couldn't be bothered looking around.
I used Chuck's Planted Tank Dosing Calculator here to set up a stock solution. Estimating my water volume to be around 350 litres I usd 55g of KNO3 in 1 litre of water as my stock solution. In 350 litres of water this equates to 0.1mg/l (ppm) of nitrate for every 1ml of stock solution placed in the tank.

I started adding 10ml of stock solution (1ppm) per day to the tank after a water change. The suggested level to aim for is 5ppm but I want to add as little as possible to get results (it's also cheaper that way). I also do not want to suddenly increase nitrates and risk shocking the fish.

For 1 week I added 1ppm of nitrate per day. No significant changes were noted beyond the plants pearling every day as opposed to only the one or two days after a water change.

For the next week I added 2ppm nitrate. The BGA is still growing fast but I am now seeing signs of a fine filament algae on leaves close to the surface of the tank. At the end of the day my nitrate test kit (Red Sea) shows the nitrate level to be less than 2.5ppm (reading is actually zero). It looks like my fast growing plants (hygro, pygmy chain sword and vallis) are absorbing all the nitrates I throw at them so far. Looks like I'll have to up the dose again.

So far the theory has yet to transform into practice. The BGA is as prevelent as always. Signs of new algae types are appearing and my plants are growing like crazy. It is early days and so the experiment will continue. How long, I don't know. I'll keep you updated.

For information:

Lighting
1 40W T8 Sun Glo
1 40W T8 Flora Glo
1 58W T5 6400K Daylight
1 58W T5 Plant Pro

DIY CO2 injection giving approx 15ppm

WK

 

[Waterloo Kid]

Here's a picture of what I'm up against. The new leaves are relatively untouched but anything older than about a week is smothered. My plants have stopped pearling now, even with a 4ppm nitrate addition per day. Makes me think that something else is limiting growth now. No obvious tell-tale signs of other deficiencies.

WK

 

[TwoTankAmin]

You should be trying to maintain a balance between nitrate and phosphate with a ratuio of between 10 and 15 to 1. Look at potassium as well.

BGA is not algae, it is a cyanobacteria. Use a small syphon to remoave as much as you can manually, then hit the tank for two days with EM at the label dosage. On the 3rd day do a water change, vac off dead bga, rinse media and it should be gone.

 

[Waterloo Kid]

Thanks for that Twotanks.
I was aiming at a 10:1 ratio as per the Redfield ratio. Things have gone rather wrong though and this experiment is over for now.
I went to be last night and everything was fine. Woke up this morning and there were dead fish everywhere. I think I've lost about 10 fish and anything up to 8 shrimp. Best I can tell is I had a massive pH crash overnight. pH was off the scale at below 6.0 All other parameters were within limits. Nitrates were at 2.5mg/l (I dosed 4mg/l yesterday evening).
Until I find out what went wrong I'm not going to dose anything including CO2.

WK

 

[iggy01]

Sorry about your fish Waterloo Kid.

Looking at your sig, I think the reason for your pH crash could have been your KH level. There is a high risk of pH swings with a KH of less than 3.

Good luck for the future.

 

[Waterloo Kid]

Yeah, that's my guess too. Funny though, I've been adding CO2 for about 6 months now. Never had a problem like this though.
If too many of my fish die I'm going to strip the tank and create a lesser planted/more rocky/more woody chichlid tank. This tank has been in it's current form for over three years and I was starting to get a yearning to change it.

WK

 

[Dubby]

Is really sad news Waterloo kid. Wish you luck for the future......