Purigen - Placement In Filter

[dazbud]

I have the APS 250litre tall tank. I doubled up on the in-hood filtration and have twin powerheads. So 1800 litres/hour moving through the flters.
 
Looking at the tank horizontally, the water looks crisp and clean. However, looking at It diagonally towards the surface, I can see very fine particulate matter in the water.
 
I had read that Purigen is 500 times more effective at removing particles than other water polishers, so I recently added a 100g bag into the filter, which is meant to be effective for up to 400 litres. However, 3 days later it seems to have made no difference.
 
I'm wondering if I have placed it wrongly, but also wondering if I am on a mission impossible. Can you achieve zero visible particles in aquarium water?
 
description of where I have placed it .... The filter consists of two spray bars the total length of the tank. They daw water from the bottom of the tank and spray 1800litres/hour of water over 4 large filter boxes at the surface, which trickles through back to the tank. Inside of each box I have a dense layer of ceramic chips, covered in filter floss. The boxes have plastic mesh lids. Ontop of the lids are filter pads. Which I have doubled up on, each with a fine pad underneath and a course pad ontop. I've just laid the purigen on the top of one of these. The ceramic chips get rinsed every three months or so. The filter floss gets replaced about every 6 weeks. The filter pads get rinsed every week (and are usually heavy with brown matter). I have been advised my tank is over stocked, but water stats are all maintained at safe levels.   

 

[eaglesaquarium]

Purigen should always be the last thing the water passes through before going back into the tank. Also, unless all the water goes through Purigen, it will not all be trapped by it.


Word of precaution: Purigen can rob your bacteria of ammonia if placed in line before the bacteria.

 

[ian]

No it can't...purigen doesn't effect ammonia, it's not like zeolite. It only has an infinity to organic waste. It doesn't touch ammonia.


Put you purigen where it gets the most contact with the water.

You will notice gin clear water in no time.

 

[eaglesaquarium]

I disagree ian.
 
From Seachem website:

Selectivity: Purigen® is the highest capacity organic filtration resin on the market. No other products can compare to its ability to clear haziness and polish water to unparalleled clarity. Unlike other products on the market which are simple ion-exchange resins, Purigen® is specifically designed to be an organic scavenging resin. When ion-exchange resins are filled to capacity by metals and other contaminants, Purigen® has barely begun to reach its potential. Purigen® generally ignores simple elemental compounds, having an extreme affinity for nitrogenous organics. The primary source of nitrogenous compounds in an aquarium is waste. Fish, corals, even plants produce nitrogenous waste. Purigen® removes that waste faster and more completely than anything else on the market.

 
You can also read this back and forth between a Seachem support person and an inquiring aquarist:
http/www.seachem.com/support/forums/showthread.php?t=2783
 
I will highlight the relevant portions:
From Seachem support:

Purigen will not have an effect on the bacteria in your tank. The bacteria will still be able to find food from newly created waste before it reached the Purigen in your filter: Purigen would effectively remove the remains of what the bacteria cannot consume (which is why there are elevated levels in the first place).
 

 
 
My answer: This person has a limited view of the question.  The bacteria WILL be effected BECAUSE the purigen will be adsorbing whatever is not used by the bacteria... or if I may say it this way: anything that gets to the Purigen first, will be unavailable for the bacteria, and the bacteria that WOULD have been using that ammonia/nitrite will as a result die off.  The colony will still exist, but the amount of the bacteria will be diminished.
 
Answer to the point by the original inquirer:

Hmmm... this is interesting. I am surmising from your answer that you consider the filter to be basically a "pipeline model", i.e., material comes in, the bacteria colony "has its fill" first, and then anything in excess moves on and gets picked up by Purigen. In such a model, it would make sense that the presence of Purigen would not affect the size of the colony, at all.

However, despite the fact that the bacteria may be "first in line" as the water flows in the filter, the water coming to them has already passed through the Purigen (on the previous "go-around", if I could use that analogy), so this seems to be more like a "closed loop", as opposed to a "pipeline model". In that sense, I'm not sure one can say who comes "first - the biological media or the Purigen. Due to the presence of Purigen there would be a lower concentration of material that bacteria can "eat", and then one should expect a smaller population of bacteria to exist in the filter.
 

 
 
 
Readdressed answer from Seachem (still showing a bit of naivete regarding the biology):
 

In long:
Bacterial population growth can be expected using a logistic population growth model, which is a mathematical expectation that incorporates the population density and the rate of increase per capita. Using this logistic growth model explains that when a population is well below carrying capacity rapid growth is seen, but as the population size approaches the carrying capacity, population growth retards. The shape of the curve would be an 'S-shaped' curve with the formula dN/dT = rN((K-N)/K). What this means is that the population of bacteria in your tank will be limited by natural factors anyway, and Purigen acts as a way to control the inevitable excess experienced even when the population is at full carrying capacity. This concept is the fundamental reason why people have problems with nitrogenous wastes; if bacterial colonies never had a carrying capacity, no one would ever have problems with any nitrogenous wastes because they would just consume all of the food (i.e. ammonia, nitrite, etc)!
 
 

 
My answer: It is correct to say that there is such a thing as carrying capacity for the bacteria.  And the thing that limits the upper end of the bacteria population is the amount of RESOURCES available to them.  If you limit the resources available, you will limit the upper bound of the bacteria.  
 
Now why does this matter?  If the ammonia is dealt with, then who cares whether its done by the bacteria or the Purigen?  Here's why you need to care: If you are relying on the Purigen to deal with a large proportion of the ammonia produced by the fish, what happens when the Purigen is fully used up and in need of recharging?  It no longer adsorbs the ammonia, and the bacteria don't have sufficient population to deal with the new ammonia created.  The result is an ammonia spike.
 
 
 
Seachem response to a correction, similar to mine above:
 

Toby_H, we will agree with you that the use of Purigen will have some effect on your beneficial bacteria. The point that Tech Support JS was trying to make is that using Purigen will not have a net negative impact on bacterial colonies(at least no more than other general aquarium practices ). Of course, we all know that some of the healthy bacteria will be impacted/removed by various means (water changes, etc). Your arguments are certainly valid, and we do apologize for the blanket statement that "Purigen has no effect on the bacteria". We do, however, feel that its benefits vastly outweigh any potential "negative" interaction with the biofilter.
 
 

 
 
In short, SEACHEM agrees that it will effect your beneficial bacteria, which was my original statement.  I am NOT saying that you should not use this product, but that it should be the last thing the water goes through in your filter, to LIMIT its impact no the bacteria colony housed in the filter.  The filter houses the vast majority of the bene bacs in your tank (although they will colonize any surface that provides for their needs), but the filter is where the vast majority are.  Its best, IMHO, to take the simple step of keeping the Purigen as the last step in the filtration process (same as you would any polishing media, anyway) so as to minimize the potential impact.  Especially if an aquarist gets over confident (almost hubris) regarding their tank with the use of Purigen.  The Purigen needs to be changed/recharged regularly.  But the schedule of that depends on how much stuff the Purigen has to adsorb and how much Purigen you are using.

 

[dazbud]

Interesting.
 
I have it in totally the wrong place them. Will change that. However, as its only in one of the four filter trays, I'm not worried that it will have a great effect on ammonia (which I can manage satisfactorily anyway). The fact that its only in one of four filter boxes could account for why I'm not seeing the crystal Clearwater expected. Effectively only 25% of the filtered water is passing through it, at most.

 

[ian]

I'm not sure about this...purigen doesn't adsorb ammonia, it adsorbs the compounds which can increase ammonia, ie dying plant mass, fish waste etc etc. the only compound available that will directly adsorb ammonia is zeolite. Purigen isn't zeolite. It's a polymer.

Their (seachem) summery is that purigen will not have a negative impact on bacterial colonies.

To the op, have a read around, Anadotal evedence only, but, there are many people keeping very sensitive fish like discus, who state 'put your purigen where you want'

Ime (I've been using it for about 5 years) is place the purigen in the best flow of the filter. I normally place mine with the pre filter at the top of the filter. It really makes no difference.

 

[dazbud]

guys, I'm not concerned about ammonia. I'm confident that is in hand and I have strong bacterial colonies in my other three filter boxes.
 
I'm on a mission to eradicate visible particles in the water and looking for advice on how to use purigen in my set up to achieve that.

also, colour wise, it says recharge after it turns dark brown. I've only had it in the tank 3 days (albeit it was in the wrong place) and its gone from light beige to the colour of fudge. I'm assuming it will get a lot darker than this in time? But I wasn't expecting it to colour so quickly especially since its meant to last 3-6 months between recharges.

 

[ian]

It doesn't normally go brown that quickly, I normally go, 3-6 months without a recharge. When using ro water it went even longer. I'm now using tap water again, and it'll last 3 months ish. You water must have been particularly dirty.

Just give it a rinse under some tap water next time you clean your filter, as some muck does come off with a decent run under tap water.