Re: [Killietalk] Top cover (was azolla was duckweed)

[Scott Davis <unclescott at prodigy_net>]

Way back when, in a FAMA article, Diana Walstad suggested that the oxygen/carbon dioxide exchange was about 100 times more efficient than in the water where those gasses are less available. Enough of those plants and they can become a bit of a "plant filter" even if they are not sequestered off in their own tank.

When I began replacing the older T-12 fluorescents with T-8s, plants responded better the the increase in light. (So did algae in neglected tanks.) Salvinia, water lettuce and water hyacinth was brought in from container gardens to over winter. The experience with the water hyacinth has convinced me that buying one of them every spring in the garden center is more cost effective for me than fiddling with them indoors.

However the Salvinia and water lettuce will dwarf to the point where they will then thrive at that size indoors. Both are remarkable in the size ranges they show, depending upon how far from the light source they are. So one gets Salvinia which looks much like the Salvinia in a backyard container out in the sun. They get smaller the further from the light, until in distant tanks and bowls, their leaves will be shrink until one's little fingernail would need a couple of them in order to be covered.

Those three plants are also "heavy feeders". The two indoor ones have been used to pretty much cover 10-gallon killie tanks and have effectively outcompeted a resident population of hair algae in a couple of aquariums, probably both by shading and competing for nutrients. Usual care still needs to be given to those aquariums. And the top cover may need to be drastically thinned. 

With such a heavy top cover, it is hard to grow any plants underneath those plants. For those and esthetic reasons I'm still very pleased with the plain old water sprite in several tanks. So long as there is some shielding from the light, the killies still seem to find places to lay eggs, which will hatch. So stronger light doesn't seem to be a problem.

Even with the understanding that we will never finds the plants together in the wild that we put into our "natural set-ups" I find natural set-ups great ways to keep killies and also to cope with a busy schedule. 

Greenwater for fry can also be considered, but greenwater is mostly a bloom of many of the protists routinely found in most fish tanks. (To grow greenwater, set up as plant tank, leave the filter without media and just for water circulation, put a bunch of defecating killies or other fish in there and forget to put the plants in there. The odds and ends fish that sometimes get accumulated can be of service "feeding" the greenwater.) Many of those organisms support themselves through photosynthesis and other feeding activities. They are not algae as such. That is why increased water changes will limit the growth of conventional algae, especially in combination with a generous planting vascular water plants and large water changes, if the lighting isn't lessened, large water changes will just result in more greenwater. Jim Thomerson estimated that those of us using greenwater, from a crowded tank of killies, to feed Daphnia, can harvest nearly 50% of the greenwater a day.

For really tiny fry like lampeyes or Ep. annulatus, they may even feed on some of those wee beasties. At the same time the photosynthetic activities will soak up the ammonia given off by modest batches of fry. I am learning to throw Moina in there with the fry. (This is cheerfully adapted from the John Clairmont "throw your Lucania goodei into the Daphnia culture" school of killie care.) The fry eat some of what the Moina are eating until they can consume the smaller Moina. As the fry grow to the point where they can ingest the larger Moina, sifted smaller "regular" Daphnia are dropped into the mix. One can add a few pond snails and feed powdered or flake food as a supplement.

Ken Combs' observation that different plants will host or carry somewhat different populations of microscopic creatures makes sense, but was one of the DOH! moments for me.

Water Sprite would be a "key" species for me in killifish
tanks...watersprite "appears" to house a slightly different microfauna 
(population) than Java moss (like serpentine worms for example)...
I would like to see this pursued. Ken thank you for that observation. Is it ok to ask where you got that info on the micro-communities on watersprite? If anyone else knows of studies on these aquarum and pond plants we have mentioned, or has insights into starting points for looking for these things (this is so out of my league) any hints would be greatly appreciated before just Googling away.

Thanks and all the best!
Scott


Dennis Heltzel <killies at fishroom_net> wrote:Generally, floating plants will increase the amount of gaseous exchange
compared to submerged plants. They are photosynthetic and so produce lots of O2 while consuming CO2. If the water or air is turbulent, then this probably dissipates rapidly, but then there will be plenty of gaseous exchange going on anyway.

If the floating plants get very dense, some air breathers might have a
tougher time fighting through it. I see this in a 55 that is choked with
Riccia. The cories have to work a bit to find a way to the surface, but
they manage.

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