The Other Little Fish
Everybody knows that fish and bicycles are perfectly complementary. Aside from building and riding bikes,
another pasttime that I enjoy is keeping fish. Hence the name of this site. Anyway, my love of DIY
extends to the wet inhabitants of my house, too. We have somewhere around fifty fish in our house (and
my office), housed in four tanks. The centerpiece in our loungeroom is a 350 litre planted aquarium, housing
a dozen or so turquoise discus, half a dozen bristlenose catfish, some cardinal tetras, and a lone kribensis,
who insists on murdering any other kribs that are put in the tank. It also contains several species of amazon
sword, chain sword, cryptocorns, and some anubias.
Stand:
350 litres of water weighs 350kg. Add in a pile of rocks and driftwood, and we have a sizeable weight to be
suspended three feet above the floor. Luckily, our unit has a concrete floor, so there was no need to take
floor loading into account. My approach when building the stand was simply to overbuild considerably, using
commercial stands as a guide.
I started by cutting six 2x4s (actually 45mm x 90mm) to the leg length, of 720mm. This height was dictated by
the height of a "D" sized CO2 cylinder. I then cut a piece of 10mm marine ply slightly bigger than the base of
the tank (by 2mm or so). I framed this with 2x2 timber, with all the corners neatly mitred. Then I cut a relief
10mm deep in the legs so that the frame would sit on a shelf on the legs. Additionally, three cross pieces were
made from 4x2s, which were screwed and glued to the plywood. In this way, the weight of the tank bears on the ply,
which in turn is supported by the horizontal frame. The legs are a press fit into this frame.
Around the base of the legs (about 50mm from the floor) I added a second 2x2 frame, as bracing. This was also set
into the legs by 10mm for additional strength.
Once all the glue had dried, this formed a strong, relatively rigid structure. I then put a back and sides on,
made from 10mm marine ply, which was glued and nailed to the legs. This braced things very well. To ensure the
legs couldn't pull out from the top, I added steel angle straps, which were screwed into the legs and top.
CO2 Injection:
It's easy for a planted tank to end up an algae farm. One takes lovely green plants home from the fish shop,
only to see them gradually wither and die. Simultaneously, huge amounts of algae flourish in the tank. Algae
is much more flexible than plants at making use of available nutrients. Plants need their nutrients in specific
proportions whereas algae is able to use practically anything. Unfortunately, fish poo isn't a well balanced
nutrient source. In order to get the plants to grow, you have to add other nutrients to get the balance right,
then provide CO2 and adequate light so that the plants can use the nutrients. Get it right, and the
plants thrive, starving the algae out of existance.
CO2 is a bit of an undertaking. You can either make the gas yourself (using yeast and sugar - messy)
or just get it in cylinders. I tried the yeast method, and gave up in disgust. I've tried a couple of sources
of bottled CO2, and can report fantastic results.
My first go was to rent a cylinder. Here in Australia, there are only a few sources for CO2 bottles.
I chose BOC gases. The rental is about $80 per year. A gas fill is $40. The smallest tank is a "D" size, which is
intended for use with welding. The size of this tank dictated the size of my stand (see above). I ran with a
rented cylinder for about eighteen months, but eventually became sick of the expense. We returned the cylinder
and watched our tank turn into an algae farm for a year or so, then went looking for a cheaper alternative.
This alternative was a modified fire extinguisher. The neat thing about fire extinguishers is that they'll sell you one.
We looked up fire extinguishers in the yellow pages, and took our regulator to the local extinguisher supply
place - Extinguisher Services, in Rydalmere. The guy there was quite familiar with "alternative" uses for their
fire extinguishers (asking whether it was for beer or a fish tank), and happily modified one for us (by cutting the tube
that would normally take CO2 from the base of the tank, so that it would deliver CO2
gas, rather than liquid. All up cost was $120. Problem solved.
The gas is regulated to a useable pressure with a simple single stage regulator. I bought mine from the same mob who
do the cylinders, to ensure compatability. It cost $77, and has a single gauge showing tank pressure, so I know when
it's time for a refill. The output from the regulator is a fixed 200 KPa.
A 1/4" NPT to 1/8" tube adapter connects the regulator to a Nupro "S" needle valve, which was the most expensive
single part, at $112. This sets the flow rate, and is adjustable down to less than one bubble per second.
The output from the needle valve goes into the canister input, where the CO2 dissolves in the water.
Lighting and hood:
The tank is quite deep, necessitating a lot of light in a relatively small area. I didn't want to have to take
the hood off for routine work, such as feeding and small water changes, so I had to leave a considerable empty
space at the front of the hood.
The hood is constructed from pine, which is mainly simply glued together. The lamps are suspended about 6cm
above the glass covers on the aquarium. I left the back of the hood open, to assist in ventilation.
Basically I have 2 * Osram 55W 4,300K power compact fluorescents, as well as a pair of 36W 5500K T-8 tubes. The
original reasoning for this slightly unusual layout was so that I could get the bulk of the light using the compact
fluorescents, and use specialty "plant grow" tubes as well. However, I've since decided that the plant grow tubes are
a complete waste of money, so I just use standard "daylight" tubes instead.
The total is 190 Watts, or right on 2 Watts per gallon. I find that gives me plenty good plant growth. Any more,
and the tank becomes difficult to maintain.
The lights are run by two Osram warm start electronic ballasts, which stay wonderfully cool. I heartily recommend
electronic ballasts.
Fertilisation:
Aquarium shops love selling you exhorbitantly priced bottles of "magic stuff". The stuff in these bottles is pretty
basic. It's easy to make your own, not to mention much cheaper. Indeed, I reckon the key to a succesfull planted
tank is to be able to tailor different nutrients.
For a wonderful overview on fertilisation of planted tanks - see
Chucks fertiliser intro.
My fertiliser uses these principles, adapted a little to make use of locally available ingredients. It's based on four
main ingredients. Potassium nitrate (potassium and nitrate source), potassium sulphate (additional potassium source),
Manutec "trace elements" mix (available from the garden center - good source of most trace elements), and Manutec Iron
Chelate, which provides additional iron. I bought the trace elements and iron from a gardening store - the rest was
from a chemical supply company. A few hundred grams or so of each will last years and years.
The Manutec trace elements and iron chelate, when mixed gram for gram, are very close in composition to PMDD (Poor Mans
Dupla Drops). The potassium and nitrate just increase the level of these nutrients, to get the nitrate/potassium/phosphate
mix about right (phosphate is plenty abundant in fish food, so I find I have to add the other two to compensate.
For our tank, the recipe that we find works is:
- 1 tsp Manutec trace elements
- 1 tsp Manutec iron chelate
- 1 tbsp K2SO4
- 1/2 tbsp KNO3
Dissolved in 400ml of tap water. 1 ml of this mix provides 12ppm NO3, 55ppm K, and 1.8ppm Fe when added to
1 l. We generally dose 5 ml per day.
For other tanks, and more importantly other feeding regimes, different things will invariably be necessary. The
beauty of rolling your own is that you can play with the formulation to get something that works for you. Just
monitor the nitrate and iron levels periodically, and adjust accordingly.
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