# DIY CO2 reactor---keep it simple...



## caywood (Apr 14, 2004)

Hey folks, 

I have just set up a new 100L tank with full Dupla-type hardware (all DIY versions). I had experimented with small home-built CO2 reactors and in-tank diffusers. The former were not ideal because of the need for a pump while I found the latter unsightly and tedious to keep clean. My final solution: 

I ran 1/8" od teflon tubing from the solenoid valve into the sump of my trickle filter. I drilled a 1/8" hole into the plastic inlet guard on the RIO pump I use for the filter return and secured the tubing so the end is just in front of the impeller inside the pump. When the solenoid trips, the tubing delivers bubbles right into the pump impeller which chews them up into little tiny bubbles which then have to traverse 3' of turbulent flow in the outlet tubing before arriving at the tank. All of the gas dissolves enroute to the tank as I don't see any bubbles at all in the filter outlet unless I really crank up the gas flow. This setup does not seem to affect the flow-rate of the pump, is very quite, very efficient, and best of all very cheap. I paid $1/ft for the PTFE tubing---so the total cost of this setup was about 3 bucks. I have extra tubing if anyone wants to buy some for cost (or trade for plants).


----------



## MiamiAG (Jan 13, 2004)

Keeping it simple is good. Nice job.

I'm interested to hear more about your other DIY projects on this tank.


----------



## caywood (Apr 14, 2004)

*DIY Dupla-style setup---cable heat, pH conrol, dosing etc.*

First, a little background:

I had aquaria 10 or 15 years ago, and was always interested in live plants. I had a 70 gallon setup with African cichlids and a lush growth of plants (just a few commonplace types: Rotala indica, H. polysperma, giant vals, red lotus and java fern)---note these species all thrive despite poor lighting. With these few varieties the tank was actually quite a verdant forest, I had lots and lots of these few varieties and with good arrangement they looked quite nice---almost an Amano sort of minimalism. The tank was stocked with only 10 Tanganyika cichlids which were never fed since they thrived by nibbling the plants---they were sufficiently out-numbered by plants to be in a good balance in their artificial ecosystem (I was gratified when I tore the tank down after 5 years to find there were then 19 fish present as they had bred unnoticed in the nooks and crannies). This aquarium was a very satisfying and relaxing hobby. Nonetheless, I had always dreamed of setting up a Dutch-style plant tank. Around 1988 I got a copy of The Optimum Aquarium. I read it cover to cover over and over. This is a great book, but also an unabashed advertisement for Dupla products. Two problems there: almost nobody in the US seemed to sell Dupla products and those who did charged very high prices. At this point in my life I was dirt poor, so spending literally thousands on Dupla hardware was just not an option. Thus began a long process of scrounging and building. I should note that I had a 12 year hiatus in aquaristics---unintentional, but I kept moving and lugging empty aquaria from place to place thinking I would set one up "next weekend". Having 12 years to find cheap or discarded components definitely worked in my favor.

TANK
For starters, I was unhappy with the sizes of aquaria commercially available. The 70 gallon I had owned was nice and had good proportions for a planted tank (48x18x20) but was not practical for one who moves frequently. All the smaller tanks available through the trade are two narrow for good aquascaping. I went to a local glass shop and had them cut pieces to my specifications (the tank is about 24 x 17 x 18" (I don't remember the exact dimensions and have a vague feeling it is actually metric---I think it is close to the size of a European 100L tank). There is a 1-3/4" hole drilled in the lower right-hand corner of the back. I found some matte black acrylic in the dumpster of a local plastic fabricator (this proved to be a treasure-trove of free acrylic and polycarbonate in all shapes and colors and some surprisingly large sizes) the acrylic was cut on a table saw with a dado blade to provide slots for surface skimming and internal construction to support a slide-out cartridge which holds aquaclear 300 sponges and carbon for prefiltration. The prefilter assembly was put together with acrylic cement and then glued into the tank with black silicone cement (also used for assembly of the tank). I should note I was concerned about using silicone to attach the acrylic over-flow box to the glass tank, since silicone doesn't really bond to acrylic too well, but it works just fine. Cost of the glass was about $50 half of which was for drilling of the hole.
FILTER
I built a trickle filter out of a discarded piece of 8" id PVC pipe about 18" long (this holds the biological filter material) some scraps of acrylic (from the source noted above) and a glass sump built similarly to the aquarium. The design of the filter is a little peculiar as the pipe is held above the sump by passing though two 1/2" thick acrylic sheets with 9" holes in them (the outside diameter of the PVC pipe). One sheet of acrylic is cemented to the sump base: I placed a 9" id O-ring around the outside of the pipe which is then lowered into the hole of the acrylic sheet attached to the sump up to the level at which the O-ring is placed. The second sheet of acrylic is added next (so the O-ring around the OD of the pipe is now sandwiched between the sheets) there are 8 stainless steel bolts that pass through the top acrylic sheet and into tapped holes in the bottom sheet---when these bolts are tightened they compress the O-ring and form a seal to the OD of the pipe thus holding it securely above the sump. The nice thing about this admittedly complicated system is that the tower containing the filter material is adjustable in height; adjusting it has allowed me to fit it into the stand and to make the filter run more quietly. (I'll try to post a picture if this makes no sense to readers) At the top of the pipe is a lid also made of 1/2" acrylic with a hole and rubber bushing to accept the inlet from the aquarium overflow. I also provided a port in the side of the filter through which I intended to pump air to aid in the oxidative action of the filter---at the moment my thought is that this is overkill and that passage though the prefilter will sufficiently aerate the water. The sump is just a glass box with a divider that separates the filter chamber from the sump where the pump is located. I had scrounged a Little Giant 1MDSC pump from some discarded photo development machinery which I intended to use for this filter, but in the end purchased a Rio 1700 submersible instead since it's quieter. As noted in my previous post the Rio pump is also my CO2 reactor. This filter cost about $35 to build plus the cost of the pump (~$40) and the BioBalls (I forget what I paid, but I think they've gotten cheaper since then). I estimate $120 total.
CABLE HEATING 
I have cable substrate heating in the tank. The problem with DIY cable heating is that if you use copper wire for the heating circuit, it has to be of very fine gauge (32-26 AWG). Such wire is impossible to find with thick insulation and is very delicate. The most common problem with DIY cable heating is breakage of the heating cable. In addition to the obvious electrical hazard, this is a catastrophe for the aquarium since there is nothing to do but tear the tank down. I was unwilling to go this route and almost coughed up the $200 for Dupla cables. However, the following occurred to me: why use copper? If you are building a resistor (which is all your cable heater is) Cu is an odd choice since the best thing about it is its low resistance. Most DIY systems use copper because its readily available---actually you can buy wire made out of just about anything---the problem is that just about the only wire you can buy with insulation on it is copper. So, if you're willing to insulate your own wire there are lots more choices. I settled on 20 gauge soft tempered type-304 stainless steel. This has about the same resistance as 34 gauge copper, but it has the added benefit great strength and corrosion resistance. I wanted a 24V system for safety and decided about 50 watts was right for my tank. This requires about 11 ohms resistance (24V at 2A = 48W (P = V x A) and 48W/2A^2 = 11.5 ohms (R = P/A^2). I chose 20 AWG SS wire because it takes about 20' to equal 11 ohms. I ordered the wire from McMaster Carr (about $5 for 250'). The astute reader will quickly see the problem here is that one can't just put bare wire in the bottom of your aquarium and hook it up to 24 V (well, I should say one shouldn't do so). What's needed is insulation. I mentioned before that I had 1/8" od Teflon tubing which I used for the CO2---the nice things about Teflon tubing are its inertness to chemicals and its excellent insulative properties. You will find actually that the more expensive copper wiring for harsh applications has Teflon insulation. So, I took the SS wire above (which has a diameter of 0.032") and threaded 20' through 1/8" od Teflon tubing (id = 0.0625). The end result is a pliant 1/8" od wire with very tough insulation and the resistance I needed. This was hooked up to a 24V 100W epoxy-encapsulated transformer (part no. PH100JG from www.CONTROLPOWERTRANSFORMER.com at a cost of $23). Now, for full disclosure, I have to mention it took the better part of an hour to push the wire through the tubing. Very tedious and frustrating---things are quite easy at first, but the more wire one is pushing the more difficult things become so that by the end, it was a struggle to get each additional 1/16" to go in. I think it would be nearly impossible to make a cable longer than 20' by this method, and if one wanted a higher wattage, the corresponding thicker wire would probably be even more difficult to deal with. Nonetheless, the results are very satisfactory, I threaded the newly made cable through a piece of plastic cloth with a 1/4 by 1/4 inch grid (the type often used for erosion control in landscaping projects---I found mine in the trash, but I imagine it would be cheap to buy) which had been precut to fit the bottom of my tank. With a little trial and error the cable was woven through the plastic grid to arrive at a more-or-less evenly spaced serpentine pattern with both ends terminating in the same corner of the tank. The heating cable extends about 6" beyond the aquarium surface and is currently connected to the power with nylon insulated crimp-on spade connectors (I'm looking for water-proof fittings for a permanent and less dangerous solution). The transformer is located in the aquarium stand and is wired into a 1/32 DIN digital temperature controller ($50 on eBay) The temperature is measured by a thermocouple which is buried in the gravel and is set at 26C with the assumption that the water will remain a degree or two cooler. The implementation of the digital temperature controller required a bit of wiring and I used an external solid state relay since the transformer is an inductive load and might have overloaded the 1A relay in the controller. For safety the controller and relay are contained in an enclosure (actually the enclosure I used was the ballast enclosure from a no-longer-functional Helios fluorescent fixture). After a month or so of running it seems the 50W cable is sufficient to heat an aquarium this size---I will add a backup heater set to 24C to the filter sump during cold months. The total cost of this setup with cable and digital controller was about $100. 
CO2 SYSTEM.
I bought a nice digital industrial pH controller with probe for $75 on eBay a few years back. Most of these industrial controllers have temperature compensation and will not operate without either an RTD temperature probe or a dummy resistor---mine has a 100 ohm dummy resistor ($0.29 at radioshack). I was lucky enough to find a 20lb CO2 tank (full!!!) in the trash behind a defunct restaurant. I had a CO2 regulator that my employer was discarding a few years back and a box of solenoids from which to choose (by virtue of being a pack-rat). Add a few Swagelok fittings 4' of 1/8" Teflon tubing and voila digital pH control. The probe was calibrated with pH 4 and 7 buffers in the usual fashion and is located in the aquarium. CO2 is injected right into the RIO pump used for the trickle filter (see earlier post). This setup cost less than $100 but only because I was lucky (and patient) enough to find everything I needed second-hand or free. I see new digital controllers are now available for <$150 but digital pH control CO2 injection should still be regarded as a luxury.
FERTILIZER.
I bought a Kangaroo brand IV feeding pump at a hospital auction years ago for $45. A friend who is a nurse was good enough to get me a tubing set for the pump. I use DuplaPlant 24 and dilute it into a 1000 mL bottle. I modified the tubing set for the pump by discarding the IV bag and attaching the ubiquitous 1/8" od Teflon tubing which is plumbed to the bottle of diluted fertilizer. The pump is set to deliver 2 mL/hr (336 mL/ week) so I have to recharge the bottle every 2 weeks or so. I am still trying to determine the correct dilution of the DuplaPlant 24. Currently I put 45 drops in 1L so I am adding the equivalent of about 2 drops per day. Some time ago a gentleman was selling these same feeding pumps online for use in reef aquaria---he was listing them on eBay and also selling directly from a website. I haven't checked for a few years. I presume there are a lot of decommissioned feeding pumps around on the surplus equipment market. 
SUBSTRATE:
Washed gravel from a nearby river with Duplarit K in the lower third. Cost: $20 for the laterite.
LIGHTING 
This was an item I compromised my DIY principles on: I purchased a Helios 2 x 55W compact fluorescent fixture about 2 or 3 years ago (an optimistic act since it was still to be years before I set up the tank). I used the lights to grow seedlings for my garden and the ballast pooped out after about 100 hours of use. The manufacturer of these fixtures seems to be defunct at this point, and I gather from a few threads I've read on-line that my experience was not unique. Therefore, the light became a DIY project despite my efforts. I bought an Advance brand electronic ballast from a local electrical supply house ($37 special order) and wired it up to the fixture. This required some modification in the fixture since the original ballast provided power to the lamps via 4 wires while the new ballast requires 6. I got some 8 conductor 20 AWG sprinkler wire from Home Depot and used one of the extra conductors to ground the fixture. The fixture works well with the new ballast, but the reflector throws light all over the room and will need to be modified at some point. The aluminum enclosure that contained the original Helios ballast was too small to contain the new ballast. I therefore used this slick little enclosure (with grounded power cord and switch) to contain my digital temperature controller and relay. The new ballast is currently screwed to the underside of the tank stand, but will be placed in a grounded enclosure at some point (right now it ruins our radio reception whenever the aquarium lights are on). It is a shame these Helios fixtures were not better made since they are very nice looking and were reasonably priced (I think I paid $119 with two 7200K bulbs included). The lighting turned out to be the single most expensive part of my setup costing about $170.
STAND
Another DIY compromise, I bought an IKEA cabinet for ~$100 since I didn't have a woodworking shop at the time.

CURRENT STATE OF AFFAIRS
The tank is up and running with all systems described above operating well. I have just added plants, two Siamese algae eaters and two small corydoras---so far, so good. The tank was planted yesterday and still has that pet-store sale tank look to it. Hopefully in a few weeks things will start to look more natural.

I HOPE THIS IS USEFUL TO SOMEONE&#8230;
I'll try to post some pics if anyone is interested. I realize the above-described method of setting up a tank is not for everyone. I was able to do everything cheaply mostly by virtue of accumulating parts and pieces over the better part of a decade (along with a penchant for shameless dumpster-diving). Nonetheless, I hope there are a few tips in there that will help somebody out. I have lots of 1/8" Teflon tubing left which I would be happy to barter for plants or other goodies if someone wants to try out any of my uses for it. It is available from most industrial or scientific supply houses as well but you typically have to purchase 50' rolls at about $1/ft.

Regards,
Caywood


----------

