JW;
Here's my take on this.
1.) can't put the tank in front of a window due to algae growth due to not having the Marine life to keep in check.Right? same problem for people with hydroponics whether using a flood method or float method or even a wick system ( I use all 3 in the winter).
Okay ,
As many have said: you would be better off going with deep-cycle batts. If your into Marine life then you should have access to places with boats, or atleast know someone who does. Go see them about deep-cycle batts.
The SLA are going to cost more anyway. I have two rows of 10 SLA's , got'em free, only reason why I have them , and they don't even come close the amount of energy they can store.
Go with the Cycling side of recharging the batts, this way you get exercize and the noise for the running faucet doesn't get on your neighbors' nerves. If the water there is that bad you wouldn't want it anywhere near something you've built and would like to keep/ reuse; Also less hassle for trying to keep the electronic dry.
If you get the SLAs for free then by all means use them but make sure that when arranging them into load banks , to keep them in similar volt & Amp hours ratings. This way you'll have less problems with keeping them all equally charged.
Also, don't let the SLAs get hot from sun light or your bulbs as they will dry up and crack.
BTW: What kind of fish?
Bruce S
PS if you can't already tell, people here giving out free advise tend to want to get right to the point. We can egt short tempered, including ME, but we all will help as much as possible and do care dearly for the environment. IF we didn't we wouldn't be here.
Good luck on your testing.