passive hydroponics pots
passive hydroponics pots

It’s been difficult with the emersed plants on the Shrimphaus shelf.  Some descriptions of the tribulations below.

Growing on the slate surface directly (doesn’t work)

First I tried simply tying Chirstmas moss down in the flow on the riverbed to see if they would grab onto the river bottom, but that didn’t really work – it seems they need something for the roots to hang onto.  Even though Christmas moss roots can grab onto surfaces, they didn’t do that in this context and the green parts didn’t really thrive either.  I’m now growing Christmas moss completely submersed in the Shrimphaus and it seems to be doing reasonably well.

clay balls
clay balls

Clay balls roll away (doesn’t work)

So, this could have been obvious, but nearly perfectly spherical clay balls won’t say put in a swift-flowing water current.  They all immediately washed away into the tank.  Also, although these are sold as ‘hydroponic grow media’ what I was hoping for was LECA – lightweight expanded clay aggregate – which is frothed up with air holes and texture to retain water, but these clay spheres are smooth and solid and don’t seem to hold much moisture.

Lava rocks don’t stack and stay too wet (doesn’t work)

lava rock
lava rock

The next attempt was small pieces of irregularly shaped lava rock.  The lava rock doesn’t just instantly roll away and can be successfully piled up.  The odd piece does come lose and escape, but at least you can make a pile of lava rock in the current.  The issue with these is that unlike the clay spheres, the lava rock stays really wet.  I made as high a pile of these as I could without them falling over into the tank and the top of the pile was still completely saturated with water.  I tried growing both Echinodorus grisebachii ‘Tropica’ and Anubias coffeefolia sitting on top of the lava rocks, but the wetness was rotting both of these plants and I suspect also drowning the roots.  This was at least partially successful for a while as both the echinodorus and the anubias put out a few new leaves (before the rot set it) so at least there is some potential promise.  I think the top of the plant needs to kept drier as do the upper parts of the roots for this to work.

Aquaponics

Anubias coffeefolia
wick hydroponics – wick ‘feet’ sticking out the bottom

Combining an aquarium type system with a hydroponics set-up is termed ‘aquaponics‘.  Since it is the emersed plant part that has been problematic I’ve been browsing literture on how to have a successful hydroponics part.  There are a number of proven techniques, none of which resemble the setup on the shelf of the Shrimphaus, naturally.  I’m giving a go to passive wick-system hydroponics, where inert media, in this case the clay spheres, is kept moist by the proximity of a wick that can carry water from the base of the container to the top.  The wicks used here are cut up strips of an automobile synthetic chamois cloth – this part seems to be working really well.  Three wicks seem to be needed to keep the clay balls reasonably moist/damp without being altogether wet.  The echinodorus and anubias look pretty sad in these pots so far, but they might rally…

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.

Particularly after a water change, the shrimp like to collect on the river run shelf.  I’m not sure what they’re after here, but this is a consistent behaviour of theirs.  This is the kind of thing you’re not going to be able to observe without a shallow flowing water component to your shrimp habitat – something which I suspect is pretty unusual.  They also like to sit in the flow generally, but the water change seems to really get them going.  Others have seem similar behaviour from their shrimp during water changes.

Cherry shrimp generally stay in the water

Here’s an interesting example of a bloody mary shrimp (Neocaridina davidi) lifting itself out of the water.  Fortunately, they don’t do this very often and are sensible enough to get back in the water directly.