Just to follow up Clive's post, these plants are listed by tropica as being able to survive in temps of 30. If you could run the tank as 28 this list would increase quite a bit.
Anubias barteri ''coffeefolia''
Anubias barteri var. angustifolia
Anubias barteri var. barteri
Anubias barteri var. caladiifolia ''1705''
Anubias barteri var. nana
Anubias barteri var. nana 'Petite'
Aponogeton crispus
Bacopa australis
Bacopa monnieri
Barclaya longifolia
Cryptocoryne beckettii ''petchii''
Cryptocoryne wendtii ''brown''
Cryptocoryne wendtii ''green''
Cryptocoryne wendtii 'Mi Oya'
Cryptocoryne wendtii 'Tropica'
Cryptocoryne x willisii
Cyperus helferi
Echinodorus bleheri (bleherae)
Echinodorus cordifolius ssp. fluitans
Echinodorus 'Ozelot'
Echinodorus 'Ozelot' (Green)
Echinodorus 'Red Diamond'
Echinodorus 'Red Flame'
Echinodorus 'Red Special'
Echinodorus 'Rosé'
Echinodorus 'Rubin'
Echinodorus tenellus
Gymnocoronis spilanthoides
Heteranthera zosterifolia
Hygrophila corymbosa 'Angustifolia'
Hygrophila corymbosa ''Compact''
Hygrophila difformis
Hygrophila guianensis
Hygrophila polysperma
Juncus repens
Lilaeopsis macloviana
Limnophila aquatica
Ludwigia helminthorrhiza
Ludwigia repens 'Rubin'
Microsorum pteropus ''Undulata''
Microsorum pteropus
Microsorum pteropus 'Narrow'
Microsorum pteropus 'Philippine'
Microsorum pteropus 'Windeløv'
Nesaea pedicellata
Nymphaea lotus (zenkeri)
Phyllanthus fluitans
Pistia stratiotes
Pogostemon helferi
Rotala rotundifolia
Rotala sp. ''green''
Rotala sp. ''Nanjenshan'' (Mayaca)
Salvinia natans
Shinnersia rivularis
Shinnersia rivularis 'Weiss-Grün'
Vallisneria americana (gigantea)
Vallisneria caulescens
Vallisneria spiralis 'Tiger'
Sam