Diy Protien Skimmer For Fresh Water

[RipSlider]

Hello,

I've been thinking for a while how great it would be if there was such a thing as a protien skimmer for fresh water tanks.

I know that this gets discussed quite a lot, but I've been having a good think and am planning to build my own DIY protien skimmer for my 600l tank just to see if they can be made to work. If they can, there ar ereally significant benefits.

I wonder if guys could have a look at my thoughts and give them a sense check before I spend money and start building.

Whenever people ask about "can I use a skimmer in FW?" there seem to be two responses:
1) It won't work becuase the bubbles are too large in fresh wate to be useful
2) It won't work becuase the salts in the marine setup mean that the skimmer is far more efficient.

After pestering my chemistry friends and delving into the less than fascinating work of bubble mechanics, I'm thinking that the issues can be over come to the point where a viable, very useful protien skimmer can be produced.

Let's look at each of the issues:

1) Bubble size:
From what I read, the disolved solids, for example salts etc, have very little effect on the bubble itself, and therefore it's size. What it does have an effect on is the media that produces th bubbles. I won't go into a crash course in "free surface enery" here, but it seems to matter a lot. The salts help increase the free surface energy of the water ( a good thing ) but also LOWER the free surface energy of the substance creaing the bubbles ( the air stone ) ( a VERY good thing indeed ) In freshwater, there is a low water surface energy and a high surface energy on the bubble stone, meaning big bubbles. A bad thing.

There has ben a fair bit of research on lowering this free energy in the bubble stone, and some new substances have been created. These give cloud of bubbles very similar in size and amount to the best impellor driven marine protien skimmers. These are now available for import from the US for about £40

2) Hydrophilic forces.
Protiens ( and lots of other chemicals ) have a "wet" end and a "dry" end. The dry end likes to be dry. The wet ends loves to be wet. When ther are bubles in the water, the dry end of the chemicals end up on the inside of the bubble wall, while the wet end stays in the water. When the bubbles move up, the chemicals are effectively moved. If there is a collection cup at the top, they can be easily removed.

Salts help this a great deal, but electricity and magnetism should also be of assistance.

The magnets would need to be very big indeed, far too big fo a garage. However, I believe that 12V DC at a lowish amperage passed through the water would be enough to effectively polarise the water in the column, hence making the Wet ends of the chemicals moe likely to stick into the water, and by consequence helping the "dry" end move into the buble surface.

This won't be as good as salts in the water, but should prove very useful.

Therefore, what I'm thinking of is something like like this:

A large tall column with one of the US bubble producers at the bottom, powered by a quiet airpump. An acrylic tube extends above this vertically to the hight of about 2 foot. Atop of this there is a collection cup, much like a niormal protien skimmer.

Inside the main tube there two bands of some sort of intert metal, one which is negatively charged and one of which is positive. The water passes through these rings on it's way to outlet.

Water is injected into the column in such a way that it is forced downwards and around, like a counter-current skimmer is normally built.

This should mean that there is situation where there is a skimmer, filled with fresh water, but with a very small bubble size with a propensity for it's "bad" molucules to bind to the surface of the bubbles.


I think that I can do the lot for less than £200, which is about what a marine skimmer would cost.

So, what do people think? Can you see any problems? Can you see any way of making it better?

Thanks

Steve

 

[andywg]

The first reason is why? This will not stop nitrate production so will not stop the need for waterchanges (suych as developing an anoxic filter might). Though I am interested to see how this would be handled.

Getting a clear tube to see what is going on is very hard without spending some serious money. For any decent width (6" or more) then a 4 foot section of acylic tube will cost a lot.

A simple counter driven skimmer usually needs to be very tall to handle this nicely (6 foot is generally considered a good size). You really want recirculating, and most large scale marine skimmers use the recirc pumps to put water in through a venturi just before an impellor.

Strangely, when looks into the science of skimming the best skimmers are tall air stone driven ones as venturi and needle wheel skimmers do not get trhe optimum amount of air into the skimmer, though I digress, and here it is more about a workable solution than the ideal one.

I am interested in how the bubble producers work. Any links?

Hmm, if this did work, then you have a great way to force huge amounts of gas exchange as well as adding the possibility of dosing with Ozone...interesting. I am very intrigued...

 

[RipSlider]

Andy,

Many thanks for thoughts. I think I can answer all/most of your questions.

Firstly, as to "why have a skimmer" I guess my initial answer is "why not"? However, at a deeper level I want to give my fish the very best water conditions that I can create for them. In the last few days, I've added a ventrui to my powerhead on my big tank, and when I look at the tank from beneath I can see an oily film where the bubbles settle. I want to get rid of this, and also any other nasty junk that is in the system. Here I'm following the advice of a chap at the lfs that I really respect. "If you can get the rubbish completely out of the system BEFORE it breaks down, it's better and easier for everyone"

Having seen the muck that comes out of marine skimmers and the black foam that collects in vortex systems in ponds, I really do believe in the value of protien skimmer system in FW. I have a 600l tank, so I needed big-ish filtration anyway, but I don't believe it's possible to over filter.

As for the system itself, I've looked into acrylic costs, and it's a LOT cheaper to buy flat sheet acrylic and make a box section shape, especially as I know I guy who can get me it at wholesale cost and will cut it for me. This is also handy because the bubbler comes as a 12x12" or 12x2.5" shape and can't be cut. Because it has flat sides, it should be a lot easier to work with in general, especially for things such as adding bulkheads. 6 foot is too tall for me, even though the skimmer will be in my garage, but I guess I could strech to three foot, especially if the bubbler at the bottom is 12" x 12", which will give a huge bubble surface area.

For the bubbler itself, try this link:

http/www.alabdiffusers.com/

Also, if you go to:
http/www.quickpure.com/flothru.htm
then you will see that there is already a system using O3 and the bubbler purchasable, although in a very different form to anything we can use immediately for fish keeping. I'm already planning to run o3 through the system. When Bob Fenner himself describes something as "the most important upgrade it's possible to make to a tank" then I'm definately taking notice.

A re-circulation system could probably be added in, it's not something I had thought of but one that I can fiddle in I think with little effort. It shouldn't be too much extra work. I think ehiem do a pump that can be run both wet and dry which sounds like it os what's required. With the flat sides, it shouldn't be too hard to add in the extra holes and bulkheads.

As for reducing nitrates, I may be breaking the un-written rules here, but from what I read and what I see in my tanks, nitrates aren't that ( for a given level of "that" ) big an issue, as partial water changes can easily deal with them. As long at they sit below 20-30ppm, then everything is ok. If they are edging above that, even with water changes, then it's an issue for the tank keeper themselves, as they are allowing too much waste to be fully broken down. Either less sources of ammonia need to be introduced, or better removal of the waste products needs to be happening. However, this is my opinion alone, and may be incorrect.

There are plenty of systems, both chemical and DIY that reduce nitrates or eliminate them completely, but at the end of the day, they are still needed in the tank to some degree in order to grow plants, which I really like in my tanks.
Producing an anoxic system is not that difficult either, it can be handled either with some sort of phelum or by a 1-sided condensor system into a low pressure container that will strip much of the free oxygen. I've seen one of these built as a DIY job in a chemistry lab at Uni for some sort of experiment, and there was about 2ppm of o2 in the system, which is about perfect for anoxic bacteria. My friend adam made on for £60 and 20 minutes on a metal lathe. I can post a rough design if you like?

Steve

 

[andywg]

The only science I have on nitrates is Nitrate toxicity to five species of marine fish by Pierce, RH; Weeks, JM; and Prappas, JM reported in Journal of the World Aquaculture Society. Vol. 24, no. 1, pp. 105-107. 1993 in which it is pointed out that earlier tests have shown that prolonged exposure to nitrates over 100 ppm may be detrimental to fish.

So 20-30, or even 60 shouldn't be too bad (remember that marine fish are more succeptible to the ill effects of nitrate due to their osmoregulatory system).

The building of an anoxic nitrification zone is not too hard, they are not THAT much to buy. The problem is getting them to run right for an extended time. You generally need a pump wired to a monitor and sensor so that the pump's flow can be regulated depending on the conditions inside the chamber. This tends to add to the costs.

I am in the process of creating live rock from cement and oyster shell (for future marine tanks - why pay £12 per kilo when you can pay 50p?) and plan on trying some in my sumps to see if there is any effect on the nitrates, though the hardness and alkalinity may suffer.

I also have some sketchy plans for a DSB, though again, how well it can work in FW is a little uncertain.

I shall be very interested to see how this goes, and if you can get some nice gunge collecting in the cup. (my advice, install a drain valve in the cup so you don't actually have to lift the cup off and risk coating your self in that evil gunk).

 

[Matthew5664]

In fresh water the water is too light so any bubbles made will not produce a fome for collection. Any FW tank that dose will have so much crap in it no fish or plans would stay alive!


Surface skimming is what you want to look into to rid the film on the waters top

 

[SkiFletch]

This is an interesting discussion if I may say so. I dont remember where I saw it, but a bunch of years ago I read and saw pictures of someone using a protein skimmer for freshwater. I remember the reason he tried to do it was because the tank was full of big messy predators (forget the types) and he worried the water quality would suffer. In the end, the only way he could get it to work was with MULTIPLE recirculation pumps proceeding up the column, very hard water, and wood air stones. Even then, the low amount of skimmate produced led him to question the validity of the design.

Anyway Steve, if you try it make sure you show us pics

 

[RipSlider]

This is an interesting discussion if I may say so. I dont remember where I saw it, but a bunch of years ago I read and saw pictures of someone using a protein skimmer for freshwater. I remember the reason he tried to do it was because the tank was full of big messy predators (forget the types) and he worried the water quality would suffer. In the end, the only way he could get it to work was with MULTIPLE recirculation pumps proceeding up the column, very hard water, and wood air stones. Even then, the low amount of skimmate produced led him to question the validity of the design.

Anyway Steve, if you try it make sure you show us pics

You wouldn't be able to remember the source of your reading would you? I'd be interested to see what problems and issues he had.

The diffuser I'm planning on ordering produces a bubble size of approx 0.4mm, which is smaller than a good limewood disfuser. I'm also thinking that polarisation due to the elctric current should provide some assistance.

I know a hardcore bio-chemistry geek who dates a physics ph.D student ( who is frankly far too good looking for such a greasy haired chap ) so I think I'll have to bribe them with cheap white cider in return for them having a serious ponder about the issues you guys have raised here, which is exactly what I was hoping to happen. If they say it's not a go-er then I'll scrap the idea, but it would be good to see some calc from them first.

I'm now thinking about adding discus to a new tank which is even bigger than the current one, so I will want to be doing everything possible to keep the water as good as I can.

I hope this comes to fruition.

Steve