Doc biofilter questions

[koiguy1969]

why not go with a 55gal drum or even bigger like a 70 gal stocktank...better to have more than adequate filtration than to find out its inadequate and have to rebuild later..no such thing as too mkuch filtrstion...just not enough! and when "oversized" higher fish numbers can be maintained as well.

 

[jneg]

The nitrogen cycle really does not depend on what color the canister is. White is very good because you can see the dirt inside but some algae can grow inside (with proper maintenance its no problem). Black is good because less algae is able to grow inside and a good flashlight will let you see the dirt inside. Nitrification bacteria grow the same in clear containers (most wet dry filters) as in black or dark ones. In my many years of aquariums with wet dry systems the size of the filter most of the time was to have enough sump volume for when power went out or to make life easier with replacing water from evaporation. The thing to remember is that bacteria just needs someplace to hang on to and grow. If we are just talking biological filtration size really depends on biological load not on volume of water.

For example if you have 40 fish inside a pond the bio-filter once it is developed will be good for those 40 fish. If you go to 50 fishes then the bio load increases therefore the bio filter will need to grow for the extra 10 fishes. If from the 40 fishes you reduce them to 20 the bio filter and some of its bacteria will die until a bio equilibrium is reached. The key here is equilibrium. Mechanical and Chemical filters are very size dependent but not bio filtration wish is again load dependent. What we need to try to achieve is that very balance between fish load and bacteria. BTW these nitrification bacteria can't be seen with the naked eye that I know of and they grow just about anywhere in the pond, rocks, liner, roots of plants, etc. Some is free floating until it finds an good place to stay.

 

[STN0091]

How much water should be cycled through in a set amount of time? Half the total volume every hour?

 

[koiguy1969]

optimally, the ponds total volume should be circulated and filtered hourly.

 

[STN0091]

Hmmn. That's tricky. Right now, it takes five minutes for the 55 gallon barrel to fill up. With that five minute holding time, that's about 660 gallons going through it per hour. Putting in a stronger pump would run more water through the biofilter, but the retention time would drop and it already seems low as it is at five minutes.

 

[koiguy1969]

my water has a 3 minute minute 'hang time' in filtration and my water parameters are always ideal and my water gin clear...thats on a 1200 gal pond and around 300 inches of fish in there....i run 1200 gph thru my 70 gal filter..... and in winter 1000gph thru my 55 gal drum filter on my basement pond.

 

[Catfishnut]

I am probably too late to assist STN with this advice, but here are some of my finds / tips to help out in the future:

Not many adhesives adhere well to HDPE (High Density Poly Ethylene) plastic, which is what most all plastic drums are mfg from. Actually, there is NO adhesive that is truly made for this purpose because HDPE has a restrictive polymer string constitution. This means that these plastics are chemically resistant to solvent based adhesives. Their rather inert quality is what makes them desirable for specific uses (since chemicals do not bond, adhere or absorb into them).

3M has a few products that will work fairly well. See my pics below for what I used for my system (5200 Marine Sealant/Adhesive). This adhesive works like RTV, but it is a polyeurethane based product and requires 7 days to cure fully. But, it will actually cure under water. I let it air cure for three days before trying it with water in the tanks and it worked very well. Cheapest place I have found for this adhesive is Jamestown Distributors Boating and Building Supplies. About $13 per 10 oz cartridge.

3M also now has a plastic adhesive that will join polyethylene. The Mfg. No. is 4693, or 4693H for a thicker glue. Several industrial supply catalogs carry this or you can locate it on the internet. It runs about $7.00 or $8.00 a 5 oz tube. It sticks to the poly quite well but does not make a chemical bond. The adhesive and poly must be above 65 degrees when using. To use put an even coat on both surfaces. Let dry until tacky but does not transfer when touched, takes only a few seconds, then press together.

For the most part, when attaching fittings to HDPE plastic, you need to use mechanical fasteners (i.e. screws, bolts, threaded fittings with seals, etc.) See the fittings in my attached pix below. These are PVC electrical conduit fittings. Use these instead of standard PVC threaded fittings because the threading is not tapered and does not bottom out. This way you may tighten the fittings snugly against the wall of the HDPE tank. You can use a large O-ring on the water side of the tank to seal it or use the 3M 5200 marine sealant, but I don't recommend using both. I tried this and the O-ring just got pushed out of the way because the sealant lubricated the O-ring and allowed it to slip out of place. I opted to remove the O-rings and just use the sealant alone. With the mechanical force from the threaded fittings, this sealant remains in contact and forms a watertight seal that won't dislodge with vibration. I used the 3M 5200 sealant on all the fittings in my tanks.

Here is a video of another adhesive that REALLY works well with HDPE, check it out as it is quite informative.

http://www.tapplasti...521014995032tim

Gordy

 

[Catfishnut]

As for the other questions... Color of the barrel, etc. I would think that the black plastic barrel would be better. UV light from the sun might kill these bacteria, so the darker the barrel is, the better. Either that or enclose the barrels or place them in a shaded area. The bacteria like a specific temp range, so you would want to monitor this and try to maintain the temp in the bio-converter tank in that temp range. If you are in a cold climate area (zone) the black barrel might be beneficial to you as it would keep out the UV, but absorb the IR and warm the water. If you are in a hot location, then it might get too hot and you would need to shade the barrel/s.

For the clearance at the bottom for the "muck". I don't think this is critical. Leave enough room for your incoming pipes and that should be plenty. I would assume that you would be using at least 2" PVC piping, so allow an inch above and below that or about 4" - 5" total. You desire a little clearance above and below the piping so that the water can flow freely and drop out its sediment load, but I don't think you need much more than that.

Gordy

 

[Waterbug]

Goops
Gordy you're so right on nothing bonding to HDPE plastic. Welding is the only way to bond HDPE. But then you add 5200 Marine Sealant which also doesn't bond?

I think for the most part all these different goops and globs aren't hurting anything because if the fitting is tightened correctly all of the goop is squeeze out and you do get a PVC to HDPE mechanical bond. So most people will not see any leaks. In the worst case the fitting won't be tightened enough and a very thin layer of goop will remain between the PVC and HDPE and over time it can leak due to shrinkage or bacteria infiltration.

Washer would be better.
If someone wanted to be "safe" a rubber washer is a much better choice than any goop. The rubber washer is exactly designed for this application. Like the O ring Gordy mentioned. But HDPE is soft enough to not need a washer.

Lock nut instead of female.
I use the electrical conduit also but instead of the threaded female adapter I use a metal conduit lock nut. For conduit applications the female is fine because not a lot of pressure is needed. But a lot of pressure is needed when used as a bulkhead fitting so I like the steel. The female can crack over time. Not common, but it can happen. With the O-ring or washer the fittings don't have to be as tight, so that would help. The lock nuts are also cheaper.

Keep bacteria in the dark.
I agree on keeping the nitrifying bacteria in the dark. If a person is going to all the trouble of building such a complex biofilter why not make it the best possible home for the bacteria. The bacteria do have a defense against UV, they clump together, so the UV won't kill them all. But the amount of ammonia they can convert drops when they're clumped (Thorn).

Glue PVC joints.
Some post a while back said PVC fittings don't have to be glued when inside the tank or pond. When not glued they can come apart. They can be cramped together really well but all pipes vibrate and the risk of coming apart is great even under low pressure. Is it really worth saving a little bit of glue?

 

[koiguy1969]

in my experience, running a couple of DIY filters on my ponds,both basement, and outdoor...most pvc fittings will push fit tight enough to never need gluing inside a filter. not gluing also allows you to make adjustments in the future without purchasing new parts. mine have been in use for years and have been fine...in fact are not the easiest things to get apart. outside the filter gluing is a good ideas for the extra insurance and additional leak prevention... theres minimal if any vibration involved in the internal plumbing, atleast with a submersable pump.. certainly not enough to cause fittings to come apart. removing the muck from the bottom of your filter is as easy as the flush valve assembly, removing the muck can ease the workload on your biofilter, making it more efficient. not only is it removing the muck from the bottom, it flushes the excess thats madfe it up in and on your media. this keeps the media cleaner and allows the bacteria to get a better foothold on the media...a cleaner filter is a more effective filter. the muck in the bottom of your filter is also a breeding ground for anaerobic bacteria, parasites and pathogens that can affect the health or your fish. whereas it may not be a total neccessity its a step towards a healthier pond and inhabitants...
as far as gluing HDPE.. my brother in law manages a plastics factory that works exclusively with hdpe and ldpe ( high and low density polyethelene) and he tells me that a good epoxy can bond pretty well as long as the plastic is heated before the application...ive never tried it but i gotta assume they probably know.

 

[Catfishnut]

Goops Gordy you're so right on nothing bonding to HDPE plastic. Welding is the only way to bond HDPE. But then you add 5200 Marine Sealant which also doesn't bond?

This adhesive (3M's 5200) has some bonding strength, compared to most all others. Here is their run down of the shear strength in psi for 5200 when applied to different plastics:

Plastics/Polymers:​

Gelcoat 519​

Polycarbonate 381​

Fiberglass 362 ​

ABS 231​

Acrylic 217​

Nylon 175​

Polypropylene 55​

Polyethylene 48

You can see that it is low, but it has some adhesive quality and I can attest that it works very well. You can remove it, if you try, but it won't come off under normal use.

Here is the link to the complete document on this adhesive:

http://multimedia.3m...gVs6EVs6E666666--

For my system, I abraded the HDPE surface area with a steel wire brush/sandpaper, then cleaned it with 3M's general purpose adhesive cleaner and finally I heat treated it. This stuff is not coming off with any ease.

Gordy

 

[Catfishnut]

Glue PVC joints.
Some post a while back said PVC fittings don't have to be glued when inside the tank or pond. When not glued they can come apart. They can be cramped together really well but all pipes vibrate and the risk of coming apart is great even under low pressure. Is it really worth saving a little bit of glue?

I glue all but a few of my joints. The ones that I don't glue are those for the very end connections where I need something to be removable, but don't want to use a union fitting or don't have the space to do so. Such as inside my filter barrels where the lake screen filters / strainers attach. These connections are near the top of the water line, under no pressure and little vibration and the fish aren't in these areas, so I can easily keep tabs on them to ensure that they don't come apart. Otherwise, I ensure that I glue everything together. It's too much hassle to repair a fitting or joint after the fact - when everything is filled with water and fish.

Gordy

 

[Waterbug]

I think if goop just had to be used then the most logical choice would be one the manufacturer at least rates for HDPE and PVC. For example Pro-Poly. They rate holding at 175 lbs/sq in. This is not a water tight solvent weld because you have to sand the surfaces so they're going for a mechanical hold to stop the two materials from pulling apart. If a person thinks 175 lbs/sq in will have any benefit for the very thin area in contact for a perpendicular fitting then goop away.

I know none of this mechanical engineering junk makes any difference to any one. Glue, goop and globs will always be king in the hobby world. It's just I think it's a shame to have a much better choice like the o-ring, something designed to work, cheaper, easier, long lasting, but still want to reach for the goop which is expensive, messy, prone to error and proven (by their manufacturers) to not be a good choice.

 

[taherrmann4]

This is what makes your hobby whether it be a pond, koi pond, garden pond, whatever it is fun. You experiment and some things work some don't but there is no rule in my book about how one must do something if I want to put goop vs an o ring I do it, if not I don't. If I would have listened to the so called experts out there when I was building my pond I would have an even more expensive filter set up than I already have, if I would have found this forum sooner I would have saved myself lots of money and made my own filter or bog but I didn't and it all still worked out just fine. So I rely on what has worked for me in the past and also listen to what others suggest and make my choice.

When folks come to this forum looking for advice or opinions we state what has worked for us in the past or pitfalls to avoid does not make one right or wrong but we give our opinions and it is for them to choose which way to ultimately go.

Just my 2 cents!

 

[koiguy1969]

i just heated (warmed) the HDPE, and used aquarium silicone on all my 'thru the filter wall' plumbing, including the waterfall weirs...not 1 problem. but i used shower drains...much sturdier mounting than a bulk head type fitting.