mineral debris from an airstone
mineral debris on the wall

The airstone does a great job of keeping the surface of Shrimphaus clear from biofilm, but how it does that exactly isn’t clear.  One idea is that when the bubbles break on the surface they fling water and biofilm in random directions, including over the side of the open topped tank.  For sure this flinging of water happens, whether or not biofilm goes with it.  This leads to a gradual build-up of minerals on the sides of the tank above the airstone from broken bubbles after the water has evaporated.  I was going to be ok with that, but it turns out the amount of water flung over the side is sufficiently substantial as to wet the wooden surface of the table supporting the Shrimphaus.  Wet wood is not a good idea so this is a problem.

Try putting the airstone in the middle

I’ve moved the airstone to the middle of the tank on the bottom.  In this location the bubbles spread out evenly over the surface of the water but don’t get close enough to the sides to fling out water (and biofilm), or at any rate this happens to a greatly reduced extent vs with the airstone mounted on the side wall of the tank.  This arrangement of having the airstone away from the walls will be a pretty good test of whether the main mechanism by which an airstone removes biofilm is through simple mechanical disruption in which case the biofilm won’t come back, or rather by evicting biofilm from the tank by throwing it over the side.  If the mechanical disruption from the centred airstone isn’t sufficient to keep the biofilm in check, the usual way of removing biofilm is with a skimmer, but that’s another piece of complicated kit to have in the tank which isn’t entirely shrimp-safe and you don’t get the benefit of additional oxygenation (as much?).

The shrimp don’t seem to have noticed or cared about the relocated airstone yet.  I’ll update on the effectiveness of biofilm prevention, any residual flung-out water/mess and any emerging shrimp behavioural changes as the new set-up settles in.

Two week update:  airstone in the middle is working

It’s been two weeks now since relocating the airstone to the middle/bottom of the shrimphaus and the airstone is working great.  There has been no sign of biofilm formation and no more mess flung outside the tank.  It seems the mechanical surface disruption is preventing biofilm formation.  All together, I’m really pleased with how this worked out.  I also found a piece of slate to keep the airstone in place, even though that seemed not really necessary.

The newly planted vallis seemed to be doing poorly with the leaves suffering structural damage and since vallis is thought to be sensitive to damage from liquid carbon I stopped the daily dosing of EasyCarbo.  Stopping the daily liquid carbon is something I had been thinking about doing anyway, on the grounds that with injected CO2 gas the “carbon” part definitely wasn’t needed and I was never really sure whether the daily low dose EasyCarbo (1 ml / 40 L) was suppressing green spot algae at all.  That said, I did notice what seems to be increased aggressiveness on the part of the algae in the weeks after stopping the daily liquid carbon.  What do to?  I would like to give the vallis a fighting chance to get established…

Low phosphate does not prevent algae

Despite a lot of misinformation in the popular literature, reducing phosphate is not a way to control algae, in fact, the low phosphate will adversely affect the plants in the aquarium reducing competition for algae.  In any event, with estimative index fertilisation, none of the major fertiliser components, including phosphate, are ever limiting and it’s well established that “excess” fertilizers do not promote algal growth in aquaria.

Can high phosphate prevent algae?

There are some tantalising anecdotal reports that high phosphate can prevent algae.  I have been dosing weekly phosphate to 3 ppm, but I’m going to give 7 ppm a try and see if that has any kind of noticeable effect.  Since it was time to mix up a fresh batch of macro fertilisers, it was very straightforward to boost the phosphates by adding just a little more KH2PO4.  My current macro mix is made up to a total of 500 ml and dosed 10 ml per day on Saturday, Monday, Wednesday into a 40 L water volume tank.

Macro MixTsp / 500 mlg / 500 mlWeekly ppm
KNO32.75 tsp16.5 g9.6 K, 15.2 NO3
KH2PO41 tsp6.6 g2.8 K, 6.9 PO4
MgSO4 ⋅ 7H2O6.5 tsp 33.15 g4.9 Mg, 19.4 SO4
K2SO43.75 tsp 19.125 g12.9 K, 15.8 SO4

Overall, this works out to 25.3 ppm K, 6.9 ppm PO4, 15.2 ppm NO3, 4.9 ppm Mg plus whatever is in the tap water used for water changes, which also probably contributes a few more ppm phosphate.

They say Cryptocoryne lutea ‘Hobbit’ is a small crypt, but saying it and seeing it are two different things.  This is a really small crypt!  The original idea was to have a small plant to go in front of the Lobelia cardinalis ‘Dwarf’ to hide the rooty lower stems of the Lobelia without covering up the pretty bright green higher foliage.  The ‘Hobbit’ is listed as a maximum height of 5 cm which sounded about right, but now I think that’s too small.  The ‘Hobbit’ adapted to submerged growth easily, but after a good number of months still ranges from 2-3 cm in height.  Further, the dark brown/purple coloration of submerged form ‘Hobbit’ gets lost against the dark colour aquasoil making the ‘Hobbit’ hard to see.  To top it all off, the ‘Hobbit’ became overrun by the Marsilea hirsuta carpet, which is about as tall as the Hobbit and spreads much more aggressively.

I like the ‘Hobbit’ but I don’t think it’s fit for the original purpose in the spot.  Accordingly, I decided to try the “next size up” in crypts, Cryptocoryne parva.  That left open the question of what to do with the ‘Hobbit’ so I’ve moved the Hobbit to the front and centre of the tank.

Cryptocoryne species have a reputation for ‘melting’ if they get traumatised.  In this case they shed all their existing leaves and make it a do-over with fresh growth.  I’m hoping that doesn’t happen with these transplanted Hobbits.  The aquasoil only very loosely holds the roots such that there wasn’t much root tearing, and the replanting procedure was more a nestle-in-place rather than putting them in a hole and covering them with dirt.  I’ll keep them free of Marsilea invasion and the new venue has more illumination as well since it is more centrally located under the light and isn’t generally overshadowed by any of the taller species:  Lobelia, Ludwigia and Lysimachia.

After two week holiday – no maintenance yet

We took a two week holiday and left the fish and plants in the Fireplace Aquarium on their own recognizance.  I did an 80% water change the day we set out, gave the fish a little extra food flakes, turned off the CO2 gas and otherwise left things as they were.  The fish, plants, fish and snails were all fine.  No casualties, and in fact everything was looking pretty good upon our return.  I had expected a huge algae problem to scrape off, but that was also fine.  Turns out these things are pretty robust.  You can buy “slow release” holiday food but I do not recommend doing that; for a couple of weeks, if everything is healthy when you leave, things will be ok upon your return.  Coming back, I gave the fish a slightly larger portion of food, did another water change, turned the CO2 back on and resumed EI fertiliser dosing.

disposable CO2 gas cylinder
Clarke 600 g disposable CO2 cylinder

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.

Fireplace Aquarium top down view during water change
View from the top during a water change

Unusual view* down into the Fireplace Aquarium during a major water change.  On the top of the mountain on the right is Bucephalandra caterina, with newly installed Anubias barteri nana ‘Pinto’ further down.  The flopped over red plant is Ludwigia palustris mini ‘Super Red’ with bright green Lobelia cardinalis ‘Dwarf’ just below it.  The low green carpet at the front is Marsilea hirsuta.  Very difficult to see are a few dark brown fronds from Cryptocoryne lutea ‘Hobbit’ at the front edge on the left side and a few sprigs in the lower right corner.  The built-in air lift tube from the underground filter system is the central whitish cylinder.  At the back from left to right are the drop checker, the heater and the powerhead.  

*It’s unusual because there’s not much overhead clearance between the top of the aquarium and the bottom of the chimney breast so it’s a little tricky getting a camera in there.

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.

Nothing has really dramatically changed in the Fireplace Aquarium but I feel the green spot algae has been growing back quicker than it used to.  I was having to give the tank walls a credit-card scrapedown every three or four weeks, but now it seems up to every other week.  I tried increasing the dose of liquid carbon (a.k.a algaecide) from 1.0 ml per day to 1.5 ml per day, without noticeable effect other than using up 50% more EasyCarbo.  For sure though the hours of daylight are increasing rapidly now and even though the aquarium is 4m from the window, it is a south-facing window and bright all day long.  I’ve reduced the lighting supplied by the Tuna Sun LED light by reducing the period of full intensity light in the aquarium daily lighting sequence by 2 hours per day, so we’ll see if that helps.  I have long suspected that I’ve been providing more light than necessary so let’s give this a go.  I’m also going to knock the liquid carbon dosing back down to the original 1.0 ml per day.

Continue reading “Green spot algae in the summer”

Time lapse  sequence following major aquarium plant trim

About a month ago I revised the layout of some of the aquarium plants.  I didn’t like the look of all the stemmy/rooty bits of the Lobelia showing up against the front wall of the aquarium so I planted a row of dwarf Cryptocorynes in front to grow into a low cover.  The problem though was the lobelia were already crowded against the front.  When one of the lobelia plants came loose it was an opportunity for a do-over and I removed all the lobelia except the smallest plant closest to the left side and replanted lobelia trimmings taken from the removed mature plants in a line a bit farther back from the front wall.  Some of the ludwigia was also looking a little ratty with heavy algae cover on some of the lower leaves so I did a pretty aggressive takedown there as well.

Continue reading “Aquarium plants recover from trimming”

Aquatic plants for aquaria are commonly classed by how tall they can be expected to grow, with the idea that it is sensible to grow the shortest plants at the front of the tank, middle-sized plants somewhat further back behind the shortest plants, and the tallest plants at the very back.  In the community these are generally called, logically enough, foreground, midground and background plants.  Of course, you don’t have to follow this scheme and there might be a specific effect you’re trying to achieve by putting taller plants in front of shorter plants, but ideally this would be a deliberate choice and not something you unintentionally discover by accident.

In this video, you can see the effect in action.  On the left, at the very front bottom of the tank, low down and in the shadow of the lobelia, is a single dark green line of newly planted cryptocoryne lutea ‘hobbit’ which is expected to grow to a maximum of 5 cm.  The aforementioned lobelia cardinalis ‘wavy’, bright green and filling the bottow left quadrant of the tank, was planted six months ago and has topped out at its maximum height of just under 20 cm.  In the back of the tank, the red plant arching over the lobelia is ludwigia palustris mini ‘Super Red’ which would be around 45 cm if stretched out to its full length.  The very low carpeting plant on the right side all around the base of the mountain is marsilea hirsuta (although if you look carefully, there is another ‘hobbit’ hiding in the bottom right front corner.  The marsilea was planted over a year ago and will never get any larger than it is currently.  Some people like the look of plants that float on the surface such as frogbit or duckweed, and in a larger setup these can be effective, but I prefer not to go there in this instance.

I like the look of the different horizontal layers of plants on the left, contrasting with the verticality of the mountain sculpture on the right.  The fish seem to appreciate the differences too – if they’re nervous they can hide under the lobelia, or explore above the lobelia while still feeling a degree of sheltering protection (or at least so I project upon them) from the overarching ludwigia.