Nitrate reactor for 400 litre heavily stocked aquarium

Question:

Hi,
I am looking at nitrate filters at the moment. I see on your website that there is information on the sulpher nitrate filter.
Could you please tell me how much flow would be required for a 400 litre (heavy stocked) tank and how often you need to change the media? How do you know the media is done?? Is it just a matter of keeping testing.
Can you just keep the filter running after it has reduced the nitrate to zero? I see in your notes that with an alcohol fed filter you can keep it going... will the bacteria not stay there in the sulpher unit just the same as long as it is getting nitrate to feed on... or is it because there is going to be peaks when changing the media?
If you have a more detailed PDF or other document it would be handy. I will be doing this but I cannot justify the cost of the other units.
Regards,
Gareth

Answer:

Gareth

As you point out we sell two types of unit, the sulphur type and the alcohol fed type.

The sulphur units use sulphur balls as a food source for the bacteria and as such they are more self contained and potentially easier to use. They are also less efficient and more time consuming to set up which is probably why all of the staff in the company run the alcohol fed ones on their own aquariums including myself.

Both systems work well however as you are growing a natural biological culture of anaerobic bacteria you must have patience as it is easy to crash the colony by introducing too much oxygenated water at one time.

The flow rate through both units should be such that you turn over the tank volume every 14-20 days and with a heavily stocked system I would suggest the 14 days. 400 lts / 14 / 24 = 1.2 lts/hr = 20mls/min.

This is the maximum flow once you have got the unit working with a full colony. Initially you will start off with only 1 drip every 3 seconds and then when the water comes out at zero you increase this to 1 drip every 2 seconds and wait for a zero reading, then 1 drip every 1.5 seconds etc etc. Very slowly in this way you increase the flow by about 20% at each stage until after 3-6 weeks you get to a flow rate of 20 mls per minute. If you increase the flow by too much and introduce too much oxygen then you will crash the culture and have to go back a number of stages or even start again.

At this stage your nitrate will start to drop and ultimately get to zero - it is not actually at zero but in balance with the nitrate that is entering your water column every day.

With the sulphur units you have no control over the size of the bacterial colony that you have and therefore no control over how negative the redox will go unless you start taking out some of the food source, ie the balls. If it goes too negative you will get a strong hydrogen sulphide smell (rotten eggs) and you will need to increase the water flow to reduce the redox.

The NFP reactors offer much better control as you can adjust both the water flow and the food addition on a daily basis, allowing you to compensate once your high nitrate level has reduced right down. Commissioning is the same slow process of drip adjustment and 205 increases however the bacteria grow much more readily and it is easier to achieve the negative 170 redox where the bacteria start reducing the nitrate by utilising the oxygen part of the NO3-.

I would suggest buying one of our peristaltic pumps, PP6ML, to feed either type of reactor, especially if you have an aquarium computer with an interval function. I commissioned my NFP unit by using my IKS computer and set the PP6ML (36mls/min) to run on for 10 seconds and off for 15 minutes. This quickly dropped the nitrate in the reactor to zero. Then 10 seconds on and 14 minutes off, 10 secs on and 12 mins off etc etc. In this way I could almost make daily changes to the flow rate as I had such accurate control of the water going in.

Once the flow rate is achieved and your turnover rate is correct it is easy to control the bacterial colony size with an NFP reactor by increasing or decreasing the amount of food you feed every day. With the sulphur version it is not so easy to get that balance and many people take them off until the level increases again.

The ideal set up for ease of running would be

NFP509 P - includes a 1ml/ minute pump allowing you to feed 2 mls of alcohol 4 times per day automatically. (also requires a digital plug timer that will time in 1 minute intervals (£10 B&Q or similar)

PP6ML peristaltic pump. - to feed the water at a constant rate - (as you need about half the flow of this pump when commissioned you will need another timer, a simple segment type this time to allow you to run 15 mins on and 15 mins off thus halving the flow rate.)

Interval computer if you have one but not necessary.

This is obviously the most expensive option but will definitely reduce your nitrate to zero and require little maintenance.

The lowest cost option is the sulphur unit which will be harder and slower to commission and you may need to play with it a little more when the nitrates are finally reduced. Use on an interval computer and PP6ML would also help a great deal.

There is another simple link to similar information on our website at:
http://www.theaquariumsolution.com/sulphur-vs-alcohol-nitrate-filters

Good luck

Cheers
Stuart