fry tank problems.

i have a small fry tank of 28l i have recently set up. I started it off with an air stone filter. it was running fine but had no lights.
we added some LED lights off ebay and changed the noisy filter to a new fluval one. since i made these changes i keep getting a this layer of scum on the top. like a thin layer of wax. I have changed the water completely and washed contents & tank. replaced using water from my main tank. still the scum comes back. there is one live plant but not doing great. no substrate. since changing the filter i havent had had any fish in there just in case.
what is it???
my fry are ready to be moved but no way can i put them in there. is it the light? the filter?
please help!

It's possible the filter may be the cause, as everything else would appear to be ok.
Strip the filter down and give it a good clean and see if that solves the problem.
I prefer to use sponge filters in fry tanks as they do not generate a current that the fry have to swim against, also the fry can feed off them.
To clean the scum off the water surface cut a piece of newspaper to the size of the surface of the tank, place it on top of the water and drag it from one end lifting as you do so, the scum should stick to the paper.

well i gave the filter yet another good clean on weds. had a look today and the gunk is back on the surface again.
can i risk putting mollie fry in there? they are getting to a fair size & i cant leave them in the floater tank much longer. i am wondering if its lack of any sort of movement in the water. no airstone now. filter is gentle flow for the fry so trhey dont have to fight against flow. there are no fish in there currently.
ideas????

Try a couple of fry but remove the scum first, try to angle or position the filter so that the outlet is at or pointing to the surface. Gas exchange,( oxygen in and carbon dioxide out) only takes place on the surface, so the water needs to be moving on the surface.
Do plenty of water changes to help the fry grow.

i had the same problem with my tank not so long ago when i upgraded to a larger size, i also transfered water from old tank and put the filter in to keep bacteria going for a couple of weeks it was lightly planted with java fern and an external fluval 305
i now dont this problem but i have added some straight and twisted vallis plants which are doing well and added a fluval mini adapted to take an airline for some oxygen in the water and this seems to have cured it up to now fingers crossed

my filter it set up to a light current with just a few small ripples on the surface

i have raised the level of the filter to try to create more surface movement. i may have to put the airstone back in too see if this helps. reluctant to do this as its so darn noisy. i will get a new one soon but as I have my 2 daughters birthdays in the next 3 weeks my bank balabce wont take any aquatics purchases just yet lol!
good idea about trying only a few of the fry. this might also help improve surface movement too.
thanks everyone!

all my babies have been in the tank sine last friday and have not lost one!!!
raised filter and tank activity seems to have done the trick. they are thriving and growing heaps.
thanks for the help everyone.

What fry are you growing on?

Guppies & mollies. My kids love them!

Its good to keep the kids involved lol, I've got some lovely guppies, they are a similar shape to Endlers but are a lovely golden colour, Im breeding them at the minute

Pleased everything worked out ok. For a relaxing hobby you can sure get stressed at times! But it's worth it in the end.

oh definately worth it!
in the main tank i have over 30 fish. my kids have named them all. and they even remember the names!
their fave is a male guppy called bob!

glad you managed to get it sorted debs and glad the fry are coming on leaps on bounds

It's funny the names that the kids give to fish, we have a goldfish called Richard lol