sine waves are not a problem with solar as long as you buy an expensive converter that is made specifically for true sine wave conversion. it does not matter how you re-charge the batteries, it's how you convert the power from battery to the tank that matters. if you are serious about going this route i would make the system powerful enough that you could power your tank year round for free!!! as long as you have a couple plug in the wall battery chargers for times it is cloudy for extended periods but you still have normal house power, you should never run the batteries down.
just remember that if you want to go 24/7 self sufficient there is more to the equation than just raw wattage. because the tank runs 24/7 and the sun does not you need to figure out how many watt hours your tank uses in a day and divide by 3 or 4 to get a rough range of how many solar charging watts you need to keep the system self-sufficient.
so if your system uses 5000 watt hrs in a day figure on needing 1250 to 1675 watts of solar power to ensure that you stay self sufficient 24/7. on an average cloudless day you only get 4-6 hrs of full charging plus a few hours at the beginning and end of the day that you will get some charge, but not the full potential. then take into account that not all days have full sunlight so you have to make sure the sunny days make up for the cloudy days. the other reason you need significantly more solar wattage then your tank uses is that you have to deal with line loss, converter inefficiencies, and other variables that will affect how efficiently the power is converted.
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