Sterilizer calcs

[fishfever]

Something that I've been meaning to do for many months since I bought my UV sterilizer from Carl's store is to actually measure the flow rate to get my turnover and gph/watts.. for some reason I keep forgetting to do this during a water change, when it's easy to do. So I finally remembered yesterday.

With about 5g drained after vacuuming, the water level was low enough so I could catch the water from the sterilizer into a plastic cup. I set a 3-minute timer and counted the cups of water, dumping the cup back into the tank when it was nearly full. I counted nearly 13 cups and after pouring out a cup into a real measuring cup, I found out each plastic cup is 2.5 liquid cups measure. So doing the math it turns out I have (13 x 2.5 x 60 x 0.0625) / 3 or roughly 40 gph. It is probably a bit higher than that normally since I measured the flow with the pump and tubes not cleaned yet. Plus I have extended the intake tube to the water pump quite a bit because I wanted the water pump mounted to the side of the tank and alot lower to get better water circulation. Since I have a 5w UV bulb, this gives me 8 gph per watt. With my 26g tank, my turnover is just over 1.5 which according to Carl's article is the minimum recommended.

So I guess my question is it possible to be too low on the gph/watt? According to Carl's article I'm in the range where the sterilizer can perform parasite control and it's rare to get this low. More typical is 20-45 gph/watt. Since I'm using probably one of the smallest UV bulbs out there (5w) the most practical way to increase the gph/watt value would be to increase the flow. I could probably do this by changing to a higher flow water pump and/or shortening the intake tube and raising the pump higher. What are the advantages and disadvantages of leaving my gph/watt on the low side? Do I sacrifice anything (i.e. Redox, bacterial/fungal control) by being in the 5-10 gph parasite control range?

[Carl]

Being on the low side causes know problems.

My only advice against low flow rates per watt is in the purchase of a UV Sterilizer based on this. In other words if you purchased a UV Sterilizer of say 36 watts and applied a flow rate that came out to 1 gph per watt, this over kill will not cause issues with the aquarium (at least from any of my experiments or outside research), the only harm is to one's pocket book in wasting money on a UV that at 1 gph per watt is not going to achieve any more benefits than say 9 gph per watt.

With your 5 watt UV, this is as small a UV as possible so my point is mute.

I would also add that few pumps or filters achieve advertised flow rates once head pressure, additional appliances (A UV Sterilizer), & other influences on water flow.

You might try dropping a return line into a calibrated bucket from a full tank will give slightly more accurate measurements (the bucket should be at the same "elevation" as the tank return).

Carl

[fishfever]

Thanks Carl, I was pretty sure a lower gph per watt wouldn't hurt but I wanted to be sure. It just so happens mine appears to fall in the range where I'm getting some benefit for parasite control also. I'll probably try the bucket measurement technique for better measurement accuracy at a later date. I think my method was probably good enough for +/-10% accuracy; I dumped each cup just before it got full to compensate for the second or 2 it takes to dump and refill the cup. I'm feeling better now that I know my turnover and gph per watt numbers; although parasite control was not my primary objective, I guess it's a little icing on the cake!