Uv Sterilisation And Second Filter

[EGR]

I tried posting this question in Tropical chat, but getting no replies
I assume I wasn't at the right place. So I'll give it a go here.

I'm currently running an Eheim Pro II 2028 on my 500L cichlid tank
(just under 2m long), and I was considering getting both a second
filter and a uv steriliser. Now assuming I go for a second canister of
similar power (I'm leaning towards the Filstar XP3) and want to get uv
sterilisation, will I have to mount a lamp on both filter's, or would
one be enough? I was worried that having a second canister might
lengthen the time it takes for any given part of the water to pass
through the filter with the uv, making sterilisation less effective.
Problem with staying with a single filter is that I'm not sure it's
really doing as much work as it's supposed to: it's claimed to be
suitable for tanks up to 159USg/600L, but it sometimes takes as much
as an hour to an hour and a half for suspended particles to disappear
(and even then, how much go through the filter and how much settle
onto the gravel is unclear). And this isn't due to shoddy maintenance:
I do two 15% water changes every week, thoroughly vacuuming half of
the gravel each time. Also, consider that the tank is understocked at
the moment (it's a relatively new set up); hence my worry that this would
become a bigger problem down the road.

Cheers!
EGR

 

[andywg]

A UV needs a certain flow rate through it to function properly and kill any pathogens or free floating algae.

If you have the right flow rate from your first cannister for the UV filter, then you won't have to fit another UV, though obviously fitting a second UV would double how often the tank water goes through a UV filter.

However, a UV filter will not prevent particles from being present in the water.

 

[EGR]

Thanks for your reply!

Obviously, the uv wasn't meant for particle removal, but as an
addition for controlling algea and diseases (though so far, nothing
to report on either front. Just never too careful...).

Incidently, turns out I had this question about flow rates:
theoretically, what would be the problem of using a lamp designed for
a higher rate than what was actually achieved? Clearly, having too
high a flow-rate would decrease exposition time, and make
sterilisation less effective. But what would the problem with over
exposition be?

One reason I'm asking is because I just found a pretty good deal on a
FilStar XP4 with a stated flow rate of 450GPH. This is too high for
the turbo twist 18W I was considering, but just the lower bound for the
36W lamp. Then again, with media, the flow rate would invariably fall
under that. Still, wouldn't it be preferable to be just below the
lower bound on a higher-powered lamp than to be at or just above the
upper bound for a lower-powered one?

Cheers!
EGR

 

[andywg]

I have read that running too low a flow rate can lead to the bulb running too hot and burning up and damaging the shroud.

 

[EGR]

Hmm, not good then. Thanks, though. I'll probably contact the manufacturer then,
and see what they recommend running with that filter.

EGR

 

[EGR]

Hmm, not good then. Thanks, though. I'll probably contact the manufacturer then,
and see what they recommend running with that filter.

EGR