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Re: Low Light, Slow Grow Tank

On Sunday 11 May 2003 01:25, Kirk Melton wrote:

> Ok, all of the responses to my previous post about non-CO2 injected tanks
> has inspired me to convert the 72 gallon bowfront at my office, which only
> has silk plants in it right now, to a slow grow tank.  It has a twin tube
> strip light with two 40 watt bulbs in it.  The substrate is plain washed
> gravel, and is about 2 inches deep (I think I will have to deepen it for
> plants, right?).  pH is on the order of 7.8 out the tap, I can't remember
> the dKH or total hardness, as it has been almost a year since I last tested
> it. 

With just over 1 watt per gallon, your prospects are limited.  If the lights 
are concentrated along the back of the tank then the light there may be 
bright enough to support a reasonable variety of plants.  Your choices are 
more varied if you can add even one more 40 watt tube.  With 120 watts of 
light the tank would still be a low-light, slow growth tank.

A mature gravel substrate will grow plants, but...  If you add new substrate 
material you can help your tank out quite a bit by beefing it up a little.  
That implies a lot of work, as you probably would need to take the tank 
entirely down, add a lower layer to the substrate, then return your existing 
substrate to the tank.  The lower layer could be gravel+laterite, various 
combinations of gravel, peat and soil (potting soil works), or any of several 
different substrates (e.g. Flourite) sold for planted tanks.

> what do I need to do to get HEALTHY looking growth in
> this tank?

Keeping plants healthy-looking -- especially in a slow-growth tank -- mostly 
means very little algae, no fish damage, and deficiency-free old growth.

algae -- your biggest problems will probably come from black brush algae and 
blue green algae.  SAE's and Caridina shrimp (but not with clown loaches) are 
good for black brush algae.  For blue green algae an ounce of prevention is 
worth a pound of cure.   To me, prevention means keeping the tank clean and 
doing regular water changes.  Other people give other advice.

fish damage -- clown loaches are wonderful aquarium fish, but some of them 
damage plants.  This seems to be an individual trait, so watch your clowns 
carefully.  You may need to move them.

old growth -- getting plants to retain old leaves means making sure that they 
are fully supplied with mobile nutrients.   Fish food is the main supply of 
nutrients for most low-growth tanks.  In my experience, fish food tends to be 
a little low in potassium.  Occasional, very small doses of an iron-potassium 
fertilizer did wonders for my low-growth tanks.  There used to several of 
those on the market.  I'm not sure where they are right now.

> Should I use water column and/or substrate fertilization;

Very little if any fertilization.  Depend mostly of fish food as the nutrient 
source and add fertilizers only when there is a specific need.   Potassium 
works well added to the water column.  I prefer substrate fertilization for 
most other things.  If you add soil to the substrate or if your water supply 
is rich then you probably won't need to worry about trace element fertilizers.

> how long of a photoperiod

10-12 hours on.

> what species should I try (please, no Java Fern --
> it turns so black in my tanks with no CO2)?

With about 1 watt/gallon your choices are limited.  The "classic" list 

Crypt. wendtii and similar crypts
Anubias (barteri nana and others)
Java Fern (sorry)
Bolbitis huedelotti
Java Moss
Water sprite (Ceratopteris spp.)

If you can add another tube or if your light is concentrated at the back of 
the tank you can grow a few more plants, including

dwarf sag.
Hygrophila polysperma
H. corymbosa
dwarf lobelia (possibly)
medium-sized sword plants (e. bleheri, for instance)

The archives are loaded with testimonials about different plants that can be 
grown under low light.

Good luck, and have patience.
Roger Miller