I picked up a new drop checker from Dennerle – the Carbo Test Precision, sold by Real Aquatics. This drop checker comes in three different sizes. I got the small 20 mm version which actually surprised me by how small it turned out to be. This checker is different because instead of having a hanging tear-drop shape, this one is spherical and has a white plastic tube embedded in the middle providing an opening to the bottom. The idea here is that the drop checker solution can easily be viewed against the white background of the filling tube which provides a more consistent reading than all-glass checkers where you’re always looking at the colour of the solution against a background of something else.
I have been using an Asta 20 nano LED light on the Shrimphaus, and that’s been fine but it’s a point source light so there’s not much illumination at either the back (shaded by the river) or the right side (furthest away). Today I swapped that out for a new Week Aqua S400 Pro aquarium light.
What’s in the box?
everything from the box
The S-series comes in three different light lengths: 321mm, 421mm or 471mm. I went for the middle length S400 model.
You get the light itself with a solid yet lightweight aluminium shell powered through a generous length cord, voltage adaptor and your choice of plug ending. You also get a milled aluminium mounting bracket with six polypropylene (?) screws to hold it all together. The light mounts on an aluminium pole which comes with a silicone O-ring to hold the light in place. Finishing up the package are two plastic zip ties for cord neatness, and a QC control certificate.
You do NOT get any form of instructions either for assembly, mounting or usage. Fortunately it’s all pretty intuitive how to put it together.
I have been using 600 g disposable CO2 cylinders to provide CO2 gas to the Fireplace Aquarium and that has been pretty good. One cylinder lasts two or three months and they are a reasonably unobtrusive size. Recently though I have been going big. Welder’s Warehouse has a two extra-large cylinders combo deal. Each cylinder holds 1300 g of CO2. Surprisingly, the larger cylinders are not much taller than the 600 g cylinders I have been using so they don’t take up massively more space. The other nice feature is they come with a flat bottomed plastic collar base and stand stably upright on their own. The smaller cylinders just have the round bottom and so need to lean up against something which is always a bit of a worry.
I ran out of CO2 gas today for the Fireplace Aquarium and swapped out the old CO2 supply cylinder for a new one. I get 600 g CO2 at a time in disposable cylinders used for MIG welding, and sure enough, the empty cylinder weighed 1200 g and the new cylinder weighed 1800 g.
End of tank dump
I few weeks ago, I noticed the CO2 bubble rate had increased substantially due to increased flow rate through the regulator on the CO2 tank. Regulators are the first step in controlling aquarium CO2 and regulators work best when the pressure inside the CO2 tank is constant. Most of the time is this easy because inside the cylinder the CO2 exists in both a liquid and gas phase in equilibrium, and so long as there is any liquid CO2 at all, the equilibrium maintains a constant pressure in the tank of around 860 psi. When the CO2 is running out, however, there comes a point when there is no liquid remaining in the tank at which point the pressure of the gas phase CO2 gradually drops as it is exhausted. Single stage* regulators “notice” the pressure in the supply cylinder is dropping and attempt to compensate by opening more fully, however they inevitably over compensate resulting in increased gas flow even though the source cylinder is at lower pressure. In some cases this failure of regulation can happen quickly and dramatically and can “dump” all the remaining CO2 gas into the aquarium, poisoning the animal residents (the plants won’t be bothered however).
With my set-up the regulation failure is not so severe, and can be easily mitigated by awareness a problem might be coming and by adjusting the flow through the regulator down a little on a daily basis until the cylinder runs out gas completely. I get more than three months of constant pressure CO2 and then a couple weeks of manageable instabiliy at the end. I’ve set a 3 month reminder for myself to remind me when to start carefully monitoring the end of this new cylinder.
*Dual stage regulator alternative
A dual stage regulator is designed to maintain constant flow even if the source pressure changes and can avoid the end of tank dump that can happen with single stage regulators. Dual stage regulators are much more expensive than single stage, can be easily and erroneously confused with “dual gauge” regulators, and don’t seem to be designed for the disposable CO2 cylinders I like to use.
Today I shifted the location of the CO2 diffuser from the left wall of the tank to behind the moutain and underneath the powerhead. The atomised CO2 gets sucked up directly into the flow and actively pushed around the tank. Previously I had the diffuser on the opposite side of the tank hidden under the plants and whilst it seems sensible to put the CO2 where the plants are, because the flow pattern is circular, that puts the plants “upstream” of the diffuser last in the queue – the water has to do a full circuit to get back to them and by that time all the microbubbles have already reached the surface. Those plants can still benefit from the dissolved CO2 of course, but they won’t get any microbubbles trapped under their leaves. The diffuser is also now hidden behind the mountain, which is good, and is shaded by the powerhead to reduce algae growth on the diffuser, also good.
While I was moving things around and doing a cleanout I also took the opportunity to clean the diffuser by removing it from the tank while still active, layering on a few drops of liquid carbon, and letting that go for 10 minutes or so. Back in the tank this increased the CO2 flow rate from 120 bubbles per minute to 130 bubbles per minute, so that worked well.
The fish seemed pretty happy about the whole thing but it will take a few weeks to get an opinion from the plants and algae.
Notes: Cute video of a 5-banded barb swimming through the tunnel under the mountain. The plant growing on the mountain is Bucephalandra caterina. The carpeting plant at the base of the mountain is Marsilea hirsuta.
Managing CO2 flow rate satisfactorily is particularly difficult for smaller aquariums; it’s very easy to have the CO2 come blasting out, but a nice steady well-controlled bubbling takes some work. The usual combination of regulator and needle valve can work, and adding in a secondary flow restrictor between the two can be a big help.
Mott porous metal flow restrictors
Mott porous metal flow restrictor
Plastic flow restrictors that work “well enough” can be had for as little as £5, but I’ve always been enamoured of the porous metal flow restrictors from Mott corporation. A metal disc has hundreds of microchannels fabricated into it such that the gas has to squeeze through to the other side. By controlling the size and number of the channels and the shape of the disc, any desired flow rate can be achieved for a defined gas supplied at a defined pressure. I managed to score the pictured one from Ebay.
Fireplace Aquarium Mott flow restrictor
Mott calibrates the flow rate against nitrogen gas with an input pressure of 30 PSI which is a typical regulated gas output working pressure. The one I got is calibrated to 10 SCCM (standard cubic centimetres per minute) which is to say, 10 ml. CO2 is less viscous than nitrogen, so this restrictor outputs a flow of 12 ml / minute CO2. I find that for the 8 hours per day the CO2 is flowing through the aquarium (controlled by a solenoid on a timer) I need a flow rate of 6 ml / minute CO2, or maybe slightly less, so this is the perfect flow restrictor for this set-up. Given an input flow rate of 12 ml / minute CO2 the needle valve has no trouble at all comfortably getting the flow rate down by the remaining 50% needed. With the new restrictor in place adjusting the needle value smoothly moves the flow rate up and down, with none of the twitchiness exhibited with much higher input flow rates.
About every three weeks or so I have to give the algae a good scrapedown with a credit card blank. It involves getting essentially my whole arm into the tank with some complicated manoevering to get through the narrow access at the top of the aquarium. It takes a pretty good hour to get things sorted out. I’ve been wondering about whether it’s worth getting a magnetic algae scraper to clean the algae without having to get all wet doing it. Lots of good choices there, with some people advocating for “the flipper“, while the platinum standard (even more expensive than gold) seems to be the ‘Mighty Magnets‘ range. What puts me off is the fear that they will scratch up either the inside (or the outside!) of the tank, whereas I’m pretty sure the credit card blank is generally problem free. The other upside to a magnetic system would be getting in behind plants and decorations. I haven’t been brave enough to pull the trigger on getting one of these yet, but maybe someday…
Lots of great videos about magnetic algae scrapers, but always for glass… bad sign so much silence about acrylic?
