Re: UV filterless tanks,

[Thomas Barr <tcbiii at earthlink_net>]

> I have a UV hooked up on my 30 but it's hardly ever
> turned on.  They're handy for green water (never had
> that) and grey slime (did), but I noticed that when it
> was on for a while, the plants looked a bit sickly,
> like they needed more iron.  Don't you have a problem
> with that happening?

No.

>  I talked with Seachem about this
> issue and they said that a UV will zap iron and some
> vitamins.  
> 
> Cavan

In theory yes. 

I have a 25 gal with no filter and with a UV(on during the lighting cycle
only).

I have another identical 25 gal with a HOT magnum(filled with spent carbon
and sponge) and no UV. The lighting/gravel/CO2 on both tanks are the same.

I'm happy with both tanks and find I don't need extra iron for either tank
relative to the other. If there is a depletion, it's not that noticeable if
you add traces every 3 days.

I've added 5mls of flourish every 3 days to both.
I've added 5mls of TMG every 3 days.
I've just started adding Plantex(2 Tablespoons in 500mls of DI water) 5mls
every 3 days.
To be fair, I'd need to add these for at least 3 weeks or longer perhaps but
it's been 2 weeks in a number of runs.

I have upped both tanks to 10 mls every 3 days a few weeks ago. Not much
response, slightly better growth but noting to write home about.

Light, KH, pH, NO3, K and PO4 fairly close in both tanks. Flow was less in
the UV/no filter tank by a ratio of 1: 2.5. This should play a role to some
degree.

I'd like a smaller lower flow canister like a small Ehiem/Fluval 103 etc I
think after trying these different set ups but the extra NH4 I supposedly
will save by removing the filter and the UV destruction of traces seems to
be very small, very difficult to see/notice from a practical standpoint.

I'm still pleased with the no filter method + UV but it's nothing grand.
I'll stick to a nice little canister for small tanks or a plant wet/dry
filter. 

Back to the shop to build something else:-)

Regards, 
Tom Barr