I am including the PAR chart for a 48" Ray2:
Based on this chart, the PAR will be 73 at 18" which is at the higher end of medium light. Without a decent, consistent CO2
supply, your tank will be an algae jungle. Is this enough light for growing DBT? IMO
, yes assuming the CO2
and ferts are in great supply.
I tried DBT (HC Cuba) for a few months and all but given up on it. Would not stay rooted, even while super glued to stainless steel mesh. I do have a small clump glued to some DW and its doing fine. IT is even growing in a few terrariums I own. But I could not pull off a carpet with it. I am running 2 Finnex fixtures on separate times which deliver 65 PAR for 5 hours, ~110 PAR for 2 hours, and 45 PAR for 2 hours; pressurized CO2
, PPS-Pro ferts.