Hi Steve,...welcome to UKAPS.
As Luis mentioned there you will be generally limited with the choices of plants should you decide to go with the non co2 method. But then again,...you can always try some easy to grow plants from the website that Iain has provided you just to try your luck out to see if it might grow for you. There are no hard rules here. We have Alastair & Troi here who managed to grow a lovely foreground carpet with no co2 at all.
IMHO there's no reason why you can't heavily plant them. In fact heavily planting from the get go helps a lot during the initial phase of the tank's life. Some plants that did do well for me in a non co2 set up were:
1)Mini Bolbitis
2)Hygrophila polysperma ( Sunset Hygrophilla)
3)Varieties of anubias ( Like anubias lanceolate, nana, nana petites)
4)Cryptocorynes (You've got loads of varieties here too like cryptocoryne wendtii green, wendtii brown makes a nice focal plant because it looks kind of reddish brown, crypt lucens, crypt parva, etc). Just google up on crypts & there are quite a bit of choices there for you to choose from.
5) Nymphae rubra is another easy non co2 friendly plant. Red color. It usually takes a while to sprout new leaves. Mine took nearly 2 months but it was well worth the wait.
6) Echinodorus tenellus,..a lovely foreground plant that's worth trying.
7) Java moss
8) Aglaeonema minima ( i think it's a marsh plant)
Lighting intensity & duration as mentioned by Luis plays a very important role. You cannot overload your plants with these.
Fluval roma 90 is about 90 litres. So with your pair of t8s, you have 0.3 WPG which should be okay ( Clonitza who has lovely non co2 tanks advised me to keep lighting to 0.25 WPG (of T8 lighting) in non co2 tanks & 0.5 WPG ( T8 lighting) in liquid carbon supplemented tanks. So yours appear to be on the high side a little (if you chose to go 100% non co2) but no worries you can always remove the reflectors from your lights. Stick to 3- 3.5 hrs of lighting for the first 1 month. Always watch out for signs of too much light in a non co2 tank like plant melts, thread algaes etc & be quick to reduce the lighting intensity further by raising the light unit if possible. However if you are planning to dose liquid carbon then you are ok at your light level but i am sure you are well aware that the addition of liquid carbon means addition of appropriate levels of fertilizers & more frequent water changes than a non co2 tank would warrant.
. You must also be very consistent in your DAILY liquid carbon dosing or else you might risk facing co2 related plant growth issues.
Substrate plays an important role in a non co2 tank. Soil based substrate are much preferred. I am sure you are well aware of most of them,..if not feel free to fire away & ask as there are loads of people here who are more than happy to help you.
Hope this helped. Take care.
