UV Questions

[bOi]

Hello people, need some help with UV here. Been looking thru the forum but too much posts and the search funtion isnt working so I thought I would post a new topic as it seem faster that way.. apologies if this has been covered before.

My main goal is to get rid of all the algae in the tank. As it sits in the reception by the window, its rather inevitable that algae grows. I didnt have this problem when it was there at first, and did scrub them away and do water changes all the time. But it got out of hand and i cant scrub fast enough for it to be clean. It grows back so quick. So im into getting a UV sterlizer or clarifier.

I have seen some around but there are afew types and what I wanted to know is which one acctually works and not harm the fishes from its radiation. Ive seen those pond UV ones on trademe that connects in between the hoses of your external filter.

Then i saw some that is inbuilt into an internal filter. and there is also one that sits on top of the tank and works like your tank lights but by emmiting UV to clear the water etc.

Which type is the best one to use? Its only going into a 180L tank. So im guessing I do not need aything of a big power? Im unsure so if anyone has opinions, or have used the different types of UV methods, please let me know..

Dont want to spend a fortune on these

[Glenn]

I use a 9 watt Pondmaster on a 400 litre tank and it does a good job of keeping any floating algae at bay.Would suggest a 5 watt on your 180 litre tank.HTH

[alanmin4304]

Effective UV is very bad for your eyes so any thing that goes over the tank like an ordinary light is either bad for your eyes or does not work. Probably the latter.

[Fee]

A UV Clarifier will not stop algae growing on the glass, it will stop green water problems. UV clarifiers are still a useful addition, but will only treat items suspended in the water that passes through it.

If you wish to reduce algae growth on the glass have a look at the nutrient levels in the tank- NO3 & PO4, algae can't grow without food.

[Warren]

Yeah, I'd go with finding the cause. I run metal halides on my tank and that's about the same as sticking it in the sun. No problems with algae as long as the nutrient levels are ok. There's a very fine line though between plants growing well, correct nutrient levels and total algae problem...

Check your water source for phosphate. Check how dirty the gravel is. Look for any source of excess nutrients. If the tank has an undergravel filter, eventually the muck that collects underneath starts releasing dissolved organics into the water at a rate fast enough to cause algae problems.

To effectively keep an algae free tank in direct sunlight you'll likely need to do 50%+ water changes weekly with very pure water and have quite a light fish load (tap water may not be good enough). To make the tank algae manageable, you may be able to find a compromise somewhere between what I've suggested and what you do now.

As Fee said, the UV steriliser will no little or nothing to fix the surface algae.

[bOi]

Thanks everyone, will give it a water test to see whet the nutrient levels are at

[shiuh]

does this mean if phosphate level is low....algae will not survive?

[Glenn]

If phosate and nitrate levels are low algae are less likely to be a problem.However plants require both phosphate and nitrate to grow well therefore it becomes a matter of balance between lighting and nutrient levels along with how heavily planted the tank is that will determine algae either being controlled or blooming IMO

[mat692]

not hijacking but back to the original Q for people that use them, or have, whats the best a in line or internal? Im going to get one for my 1000L just to help so not going too big but was thinking of useing an internal in the sump or having one inline on one of the overflow hoses/ on one of the return lines/ or on a cannister that wil be running in the sump??

[alanmin4304]

I did a lot of research on UV many years ago before building one myself and there are many things that are critcal in design such as water clarity, depth of water , water movement and temperature etc. You would need to place it after the filter, have a means of cleanig it and have the water movement slow enough to give adequate contact time. If I remember correctly the operating temperature was around that of a tropical tank.

[Warren]

Yip, the magic number for UV is 4.

This means contact for 4 seconds and 4mm maximum depth of water.

From this you can easily figure out what diameter tube and length tube you need for a given flow of water. This will guarantee a 100% kill rate in the UV steriliser.

If you don't care about 100% then make it any way you like. It will still have some effect, just not as good. I made one for a 1200L tank using a 4' fluro tube with the water in direct contact with the quart. There was a 4mm gap between the quart and the inner wall of the outer tube. The flow was adjusted to give 4 seconds contact (I used 5 to be sure). It was only use to fix disease but did also help a lot with algae.

[mat692]

the internals power head would be matched to the uv Watts? and the max flow for a inline would be what its says/ ie a 3000LPH UV filter will be effective at up to 3000LPH? and is there a prob with having too little flow, do they over heat or kill off good bacteria??

Have done a little reading and after the sump is deff the way (meant to be filtered water)

[alanmin4304]

I think most are designed so the water is in contact with the UV source and is therefore cooled by the water. They generally need to have a slow flow rate to get the reguired contact time. They are sterilizers and will therefore kill what they come into contact with (they are not selective)