Purely a guess, but I think you're keeping the soil way to moist, when you have all that algae stuff growing on it.

When I start seeds from a tropical type of plant: I put them in regular potting soil, lightly water it one time, put a small bamboo plant stick in the middle of the pot and put the whole pot inside a clear plastic bag and tie wrap it at the top around the stick.

Makes a perfect environment for humidity, but not excess water in the soil.

I should of stuck with my method for the batch of Brom seeds I had.

too moist + not enough light = algae

perlite seems to promote algae growth, i have found vermiculite to be a better alternative for seedlings, but vermiculite is not a good material for adult plant soil mixes

you can try spreading fine gravel on the surface to choke out the algae until the seedlings catch up in size

I got the same problem with my Orthophytum seed-box,
then I treated them with "Physan 20", the plant looked recover
and also algae have disappeared.

On the top edge of soil on the top photo I see mineral deposits, which means there has been a lot of water evaporated from there. xreophyte_nyc is partially right. Too much water, if there was not enough light the algae would be brown. It is green algae which usually means to much light, but that is probably not the problem. It almost sounds like "damping off". Leave the cover off the container, and begin watering when the potting media looks dry, lack of air movement around the plants is also part of the problem.

Suggestions: cut back on the light some, water less, do not use a cover on the container, and put it where there is some air movement.

This is often the problem we have when raising seedlings indoors. We tend to keep them too damp, and the roots rot. There is not enough air circulation, and the soil does not dry out, which is important. The soil will dry out mostly because the seedlings are using water, but they cannot be kept wet. Seedlings of almost all plants grow better if they have good air circulation around them, use a small fan if you need too. If you ever visit a greenhouse they almost always have large fans, even if they are exhaust fans they create air movement when they are running.

I get algae on my community pots too. I use sphagnum moss as a medium, and even if I let it dry out the algae remains once it has gotten established. I have been spraying them with Green-Shield, which is essentially the same thing as Physan, which Stephania recommended. It seems to help keep it under control, and doesn't hurt the seedlings.

This is the reason I use the soil you saw in my photo's

Thanks all for the suggestions.

I have done a search on Physan 20 & Green-Shield, and, unfortunately, neither seems to be available in NZ. The closest match I could find was a Moss, Mould & Mildew product that contains similar active ingredients. So I may just give this product a try in a weak dose, & see what happens.

John, you are right, all my seedlings are grown indoors. I use small plastic containers, in aquariums, under fluorescent light. The advantage of this system is that it allows me to control temperature, and light duration year round, but the disadvantage is lack of air circulation, and constant evaporation. The NeoÂs seem to thrive in this set up, but some Vriesea, Alcantarea, etc, do start to decline after the initial 6 to 8 mths of growth. Maybe I need to rig up some sort of a fan to improve air circulation.

Another consideration in seedlings is good drainage in the growing containers so they can be flushed out properly...salt.. calcium.. etc builds up if not flushed

Devo, after the seeds germinate and get going leave the lids off. Try this, check to see if those remaining seedlings are firmly rooted, if they are not, it probably is damping off. HDD is right there should probably be some kind of drainage holes. I am using plastic tubs, with tight fitting lids, I will probably need to either melt or use my drill to make drainage holes soon. I will probably melt them using a woodburning tool.

HDD do you use pots to start seedlings? I have always started Bom seeds in deli cups with peat moss as a substrate, I am beginning to re-think this.

Devo & all,
Regarding needed air circulation for aquarium setups,my gardener friend Terri,at the bbg, came up with a good and inexpensive idea.
All computers have a small fan running to keep temps down,and they sell replacement fans at stores like Radio Shack.I believe they run on 12 volts dc,from the computer power supply,so if you provide an external 12v.battery,and connect it to the fan and hang it in the aquarium,you have your air circulation problem solved.
As for myself,in the room I use for growing seedlings,I have a 15" oscillating fan going most of the time,so that does my air circulating for me.
Bob

Stephania, I checked the Physan 20 out on the Internet. It is an impressive product. I searched every where I could think of to get it, but apparently it is not to be found in South Afica. A pity, it seems such a wonderful, all-round to product to use! Japie

You might try doing a search for n-Alkyl dimethyl ethylbenzyl ammonium chloride, and see if there are other brand names for it outside the US. It's an algicide. There are a number of household cleaning products that contain this compound, but they may have other ingredients that are harmful to plants, so I wouldn't try using any of them. Also, getting the proper concentration is important. It must be diluted according to label directions, and handled with care.

If you want to kill the algae, just stir the media around the plants, and let it dry out. I don't honestly see the algae as a problem. It is a by product of the container being too moist though. It might be unsightly, and it may be using some nutrients, but it is not a problem unless it is growing on the leaves of the bromeliad seedlings.

I'm not sure I would use an algicide either, unless you use one that is made for aquariums and safe for aquatic plants. Most call for removing the plants you don't want to kill before using it anyway.

yes bambi_too I use pots

Hi all - I thought I should resurrect this post as I have found some more information to share.
In Lisa's post of Mon July 23 she mentioned an algicide with a very long name (I won't try to re-type it as I'll probably get it wrong), However, this chemical is marketed in Australia under the name of ALGINOX with the active ingredient of Benzalkonium Chloride and is a swimming pool algicide/disinfectant.
It is available in Woolworths stores in my local area on the south coast of NSW so I would imagine it should be easy to track down anywhere with Woolworths stores. It was reasonably priced, from memory at about $20 (Aust) for a 2 litre container.
If you Google "Wikepedia" and search for Benzalkonium Chloride, you will find that it is just another name for the chemical Lisa mentioned, (maybe they thought they would make it easier and shorten the name for us "non chemists")
If you then Google 'ALGINOX' and scroll down to a PDF file "Monthly Bulletin Jan 2008" which is from the Southerland Orchid Society in Aust. In this bulletin you will find a table of quantities relating to using this product on orchid seedlings.
It was written by an orchid grower and gives quantities to use when de-flasking orchid seedlings. As they are about the same size as the bromeliad seedlings which this post is about I think from what is in this article one can safely assume that we could use the same quantities for bromeliad seedlings.
I think it's worth a try as if seedlings are already dying, what have we got to loose? I'll leave that decision up to whoever wants to give it a go.

REMEMBER TO NOTE THE WARNINGS ON THE CONTAINER AS IT IS A CHEMICAL.

All the best, Nev.