UV Filter

[Kerry]

Hi Garden Ponders

In my losing battle against the algae in my pond, I've decided it's time to invest in a UV filter/clarifier. I'm hoping somebody here can give me a bit of advice.

The smallest capacity filter at the local pet shop is for a 6,000 L pond. My pond is 3,000 L (depth is half a meter) - so in other words the UV filter is twice the strength needed for my pond.

The guy at the pet shop said this UV filter needs a pump capacity of at least 2,400 L. My pump is only 1,800 L.

Some questions:

1. If possible I'd like to avoid buying a new pump. Seeing as the UV filter I'll be buying is twice the capacity for my pond would it be ok to use my current pump? I've also heard that using a faster flowing pump can actually be less effective as the uv light doesn't have time to kill the algae as it flows through.

2. Just out of interest, how long will the filter take to clear the water of the existing algae? Right now, with the clarity (or lack of it!) of the water, the fish are visible up to about 15cm down).

Thanks for any assistance!

Kerry

 

[HARO]

Kerry; the figures given for a UV clarifier are maximums, and should not be exceeded. In your case, your water would be exposed to the UV roughly twice as long, and with the bulb producing twice the energy it would be four times as efficient as running it at the maximum, if you follow my reasoning. Depending on the amount of algae in the pond, you should be able to clear it in a few days. Keep in mind, however, that the UV simply kills the algae cells... you need a good filter to remove the dead matter from your water!
John

 

[fishin4cars]

I agree, the larger Uv with slower pump is actually a benefit in your case. The key to it being sucsessful is getting the dead algae out without killing your bacteria bed. The more of this dying Muck you can remove from the bottom of the pond as it settles and the more you can catch BEFORE it actually gets to the actual filter itself. The more assistance you will give the UV light, and the less assistance to the algae growth. It's also a good idea to do water changes regularly during this time. In most cases the algae started due to higher Nitrate levels, even though your killing the algae bloom the nitrate or food source is still there and will be increasing as you kill it off. DON"t try to super clean all at one time, this needs to be done agressively but not so agressive as to disrupt the stability of the pond as a whole.

 

[koiguy1969]

this setup would be more efficient at killing alge, pathogens,and parasites as well...its a win-win!....and remember.. if your having problems with string alge, a U.V wont help theyre just for single cell (green water) algeas.

 

[sissy]

trapdoor snails help with algae but not sure how available they are there and some use the clams too .I heard good and bad about the clams though

 

[Waterbug]

Running less water through a UV is fine as has already been said. Being more efficient would depend on your own definition. If 99% of algae is being killed in the filter at the rated flow then doubling the holding time might kill 99.2% or 0.2% more. To me paying more for the unit and electric wouldn't fit my definition of efficient. But if you wanted to kill that extra 0.2% then it could be more efficient than buying 2 smaller units.

You get a lot more options buying online. I think the days of local shops thinking they can carry a couple of options, not offer to order the needed product, and expect people to just accept that are slowly coming to an end.

As a side note...Keep in mind that UV isn't a set it and forget it deal. Sometimes they have to be taken apart and cleaned often. Many don't think they work because they never clean them. And also many people run them 24/7 when many times just clearing the water once is enough for the bacteria that kills algae a chance to grow and the UV can then be turned off. So when buying and picking an installation spot you might consider cleaning ease. Those that come with wipers can be good I think, but I've never personally used one. I've seen UVs build a calcium type deposit on the glass in just a few days and not sure the wipers would handle that.

And just to confirm, I also expect a UV to clear a pond in a day or two. But only the green. There can be a lot of other stuff in the water as well as the dead algae.

Also, being more specific than just saying "algae" can save you some trouble. Dealing with a macro algae like string algae and unicellular algae are two different deals. When people post responses they may assume one type or another based on context.

 

[Kerry]

Thanks for all the input guys!

Sorry, I should have specified... it is the single-cell algae I'm trying to get rid of.

Unfortunately the (few) online pet stores in this country don't really stock pond equipment - they seem to cater only for aquarium setups. And I'm not really keen on ordering off international sites for various reasons, so I'm kind of stuck with the local pet shop. I actually didn't ask if they could order stock for me - I'll ask them - if they say no then I'll just buy the higher capacity UV light.

I'll post back later and let you know how it goes!!

 

[Waterbug]

Is Isivande Fish Ponds and Koi Ponds your local shop? I was surprised to see them offering an 8 watt unit recommended for 6000L ponds. Inexpensive too by what we pay in the US.

These guys are online and out of Centurion.

Is the one you're looking at 8 watts? In general I'd expect an 8 watt unit to be perfect for 3000L. But I don't know the specific unit and UVs are rated by flow not pond volume. Sellers giving a pond size is just a guess. If that 2400L/hour rating is the max flow rate I'd bet 1800L/hour would be right in the recommended flow rate. Take a look at the manufacture's specs, sellers often don't know much about products, just how to sell them.

If you're looking at an 8 watt unit that's about as small as they go anyways. Going to a 5 watt would be too small.

 

[koiguy1969]

i just wanted to add that a 9 watt tetrapond UV would clear my pond in a few days (3-4) and i would run it for an extra week after waer cleared for good measure.i would then turn it off clean it and store it for the next season...i no longer use one but the 9 watter served me well on a 1200 gal pond...about 10 days a year.. thats it.

 

[appycrazygirl]

I run two in pond UV sterilizers in my pond. Both are 13w and have their own 700gph pumps built right in. The are great. I have them attached to a small brick and drop them into the pond when needed (with some adjustment with my pond net to make sure they are upright). They work great. Whats nice is that when I am not using them i just pull them out, clean them and put them away. The other thing with UV's is you have to check bulb longevity. Some models have different life expectancy. My are recommended to be changed ever other year. I purchased them on ebay. They are available in different watts also. I have a 4000 gallon pond that gets full sun most of the day and these keep my water crystal clear. Heres the info. http://www.ebay.com/itm/All-One-Pon...73?pt=LH_DefaultDomain_15&hash=item3a69ed4135

 

[Kerry]

Hi again, and apologies for the late response!

Ok, so I bought a 'Pond Medic' UV sterilizer. I have 2 questions:

1. When I got home I unscrewed the 'housing' (just for curiosity's sake), and I noticed that where some of the wires in there connect to other components, the wire is bare. Is it supposed to be like that? The housing doesn't look like it's water-tight to me... is it safe/normal for that bare wire to be directly exposed to the water?

2. There is a warning label on the unit that tells me to wire the unit through a circuit breaker. Is it necessary to add a separate circuit breaker to the cable before the plug, or would the circuit breaker on the household's DB board be ok? (all that's connected to that circuit breaker are the outside lights and the wall socket where the UV sterilizer/pump will be plugged in. How do you guys have your UV units set up?

 

[HARO]

I imagine the unit you have is not designed to go INTO the water; water passes through a quartz-glass sleeve around the bulb and exits at the other end. Therefore the wires are noy in contact with water. Read any instructions with the unit and install accordingly. And the outlet you plug it or any pond acessories into should be protected by a ground fault interrupter.
John

 

[Waterbug]

I can't see your unit so I can't answer the questions directly.

wire is bare. Is it supposed to be like that?

In general ground wires are bare. It's not a cost saving thing, it's because they work better bare.

housing doesn't look like it's water-tight

I assume your concern here is because of seeing the bare wire? I don't know the unit and you gave no link to it so I have no idea whether it should be water tight or not. Sorry.

wire the unit through a circuit breaker

I'm guessing the instructions said something more than that because that doesn't really provide any useful info.

Is it necessary to add a separate circuit breaker

Depends on the unit you have and also what devices are already on the circuit you want to add the UV to.

How do you guys have your UV units set up?

I've only ever installed UV filters with plugs. So I plugged them into the same outlet as the pump. But like I said, there is only one test, and that's checking what's on the circuit and the load the circuit is designed to handle.

 

[Kerry]

The unit didn't come with any instructions, no box, no packaging, nothing! :neutral:

I don't know the unit and you gave no link to it.

Sorry, I did try to find this model on the internet yesterday - and was unsuccessful. I'll take some photos and post them here.
What I can tell you for now is the following:
Pond Medic 8 Watt UV Sterilizer
Pond Capacity: 6,000L
Max flow/hr: 2,400 l/hr
220/240V, 50Hz

It's not just the ground wire that is bare - the live and neutral are exposed at the ends too. I've deduced that it must be an out-of-water unit. But I still don't like that the housing is not water-tight. What about rain, etc? I guess I could seal it off with silicon sealer....

 

[Kerry]

Photos as promised.....