of micro-nutrients (Iron, Magnesium, Calcium etc) while Flourish Excel™ is primarily glut. You need both types of plant
food - one does not replace the other. Flourish Excel™ can be bought in many different sized bottles from 250ml up to 4
litres.
Another source of glut is Aquagreen's “Dino Spit” (yes, that's its name - it goes with Dino Pee and Dino Poo in a set of
aquatic plant fertiliser products developed by Dave Wilson at Aquagreen, a man obviously obsessed with bodily fluids).
The Aquagreen product is available online in 250ml and 500ml bottles.
A relatively new source is G&K Lloyd-Jones' “Glut Blocks” - a clay-like block impregnated with glut that slowly
releases the chemical over a three week period. Like the other vendors, G&K Lloyd-Jones also have a macro/ micro
nutrient product, also in block form, that complements glut. Glut blocks are only available online.
My own experience with glut started in early 2013 when my automated CO2 system
started to misbehave. Rather than get it fixed (which is not straightforward), I decided to
try glut – first as Seachem's Flourish Excel and later as Aquagreen's Dino Spit. I'm now
trying the Glut Blocks. Overall, the results have been satisfying. Without changing the
lighting regime on my 70 litre planted cube – a 70 watt metal halide for 8 hours each day
– or my macro/micro dosing regime (Aquagreen's Dino Pee), the stem and rosette plants
all continue to do well, perhaps at a lower rate of overall growth but still “pearling”
oxygen late in the day. I did get some initial outbreaks of algae, particularly Cladophora,
but these stabilised after a few weeks. I have noticed large pH swings – upwards during
the day from around 7.0 in the morning to nearly 8.0 at lights-out – while using glut. I
assume this is because CO2 produced by the fish and plants during the night lowers the pH
and it is then preferentially taken up by the plants when the (strong) light is on. I have to
keep a close eye on temporary hardness (KH) to ensure these swings don't get too large.
Some plants did not take well to the change to glut – particularly some of the delicate
fissidens mosses. The worst affected, however, were the liverworts Riccia and Riccardia
(“Coral Moss”) which actually started to brown off within a few days of starting with glut. I now keep these more
delicate species, along with other simple plants like Süsswassertang (see endnote) in tanks that I am not dosing with glut.
I found no observable impacts on fish (Corydoras
catfish and Pencilfish) or shrimp (Cherries) kept in
the tank.
So far so good. Glut appears to be a viable
replacement for CO2 injection in normal planted
aquaria. I do miss the ability to manage the pH of
the tank using CO2 but this is a relatively small
price to pay for the lack of hassles with solenoids,
needle valves, regulators, diffusers and refills.
Speaking of price, that's the real difference between
the different glut products I have tried.
Only Aquagreen's Dino Spit provides detailed label
information about the concentration of glut in the
product (10%). It isn't hard, however, to work out
from the recommended dosing rates how these
different products compare on a value for money
basis.
Using them as recommended and calculating a
dollar figure for treating a standard 100 litre planted
tank gives some interesting comparisons.
Aquagreen's Dino Spit comes out as far and away the cheapest source of glut for rou