magpie said:
..stem plants? Worth it? OR not? TGM supplies plants that have been grown immersed for quite a while, which would seem to defeat the object somewhat - but 1-2-Grow are definitely emerse, so could try some of those (largely to see what happens, tbh...)
I think you might have these definitions mixed up. A plant is considered emmersed if the leaves are growing in air. This is the form that aquatic plants spend half their time in during the dry season. Most plants, including Tropica plants are sold this way. So if you place these in the DSM tank then they should just carry on as long as the roots have access to moisture. A plant is considered in the
submersed form if it's leaves has been growing underwater. There is a huge difference, so if you are being supplied with submersed plants then it's not a good idea to suddenly place them in an emmersed environment such as a DSM tank, although some plants can handle this shock better than others.
The whole point of a DSM tank is to cycle the sediment, especially if you are using sediments known to leech ammonia. ADA Aquasoil is notorious for this but some of the newer substrates may exhibit some of this. It's the cycling of the sediment that determines whether a tank is cycled or not. Everyone focuses on the filter bacteria alone, but this completely misses the point. It's the sediment that determines the maturity of your tank, not the filter, which can only handle nitrification of the water column. Poor or low sediment bacteria causes ammonia spikes, driving instability and poor nitrification. This is what gives rise to algae we see on tank startups. If the tank is kept un-flooded, then there is no algae and the ammonia excess in the sediment becomes mineralized. The bacterial populations are given a chance to build. If the sediment is stabilized, then when you do finally flood the tank it is then already "cycled". No ammonia issues and algae triggers are then suppressed. Fo ADA AS users, no leeching of ammonia into the water column.
The second advantage of the DSM is that carpet plants, which are famous for their poor adaptability going from emmersed to submeersed and their very slow propogation underwater, can be grown much more easily in the emmersed state. So the idea is to allow the carpet plants to multiply, send out roots (so you don't have the difficulties keeping them rooted underwater) and establish a connection with the sediment. Carpet plants are therefore much more robust by the time you do flood the tank and you'll have a chance for them to cover the ground without the die-off and losses typically associated with planting day.
With these two issues in mind, you can see that the addition of stems is not all that important, but their addition is not that much of a big deal either. Add emmersed stems, or crypts or swords if you want.
The humidity issue is also not really a big deal. You don't want the plants to dry out and you want to avoid mold so just keep it under controll by varying the coverage using cling film or whatever. Using a spray bottle and misting the plants regularly will do the trick. It's not that important at this stage what the water parameters are like so just use tap. If you're using Aquasoil then there is no need to add nutrients to the spray bottle but if you're using sand or other inert substrate then you can add a little to the mix. I wouldn't go through the trouble of semi-flooding. Just keep things moist an the plant roots will do the rest.
magpie said:
oh yes, except sand - hydrogen suplphite pockets happen in un-moving, but damp sand - don't they? So if I have a largeish area of sand, am I at risk of creating these?
Hydrogen Sulphide (H2S) is a product of poorly aerated sediment. This means that the normal nitrification occurs like this:
NH4=>NO2=>NO3 This can only happen if the bacteria have access to Oxygen (O) within the sediment. If there is no Oxygen then bacteria look for other substitute elements, such as sulphur, which is normally abundant in sediments.
If your plants are growing though, then they are producing Oxygen and the Oxygen production is sent to oxygenate the roots. The Oxygen then escapes into the sediment. Therefore H2S is not an automatic result of using sand. In fact it has nothing to do with sand. It has only to do with the presence (or lack thereof) of Oxygen. This ought not to be an issue in DSM. I mean, this is the whole point of DSM, to oxygenate the sediment and to remove the ammonia...
Cheers,
