Thanks to all for your helpful advice so far, much appreciated.
Now, the story so far, today have taken out the 3 offending so called non aquatic plants according to my lfs (cordyline and 2 dracena plants)
They have now been rehomed as proper household plants. Luckily my girlfriend likes household place, so no problemo!!
Also took out 2 or the 3 known pond snails. Could not find the 3rd one
But not too worried about that unless a snail boom happens!!
The plants for anyone interested are:
Java Fern (Microsurium pteropus)
Cryptocoryne Walkeri
Water Wisteria (Hygrophillia difformis)
Anubius (Anubias Barteri)
Twisted Corkscrew (Vallisneria spiralis)
Anacharis (Egeria densa)
Hornwort (Ceratophyllum subersum)
Green Cabomba (Cabomba caroliniana)
Apologies for any wrong names or spelling. Am sure someone will correct me! Lol
I have tried to work out if my lighting is suitable and according to my calculations seems to be ok.
Anyone who could confirm or correct me would be great.
I have 2x T8 15w 18000K. (1 is at 35 lux and other is 50 lux) and tank is 90 litres (23 gallons US or 20 gallons imp)
Calculated 2 x 15w = 30w then 30 divided by 90lt = 0.3 to 0.4 watts per litre (1 to 2 watts per gallon)
I think this is basically low lighting so should be suitable for these plants
Had to change layout slightly but I think looks pretty good