I have low ph in my nano (7.7-8.0) because of excess co2. I live in south Florida so I can't leave windows open. I don't have a skimmer so I can't use a co2 scrubber. The corals are doing fine overall. So a refugium seems to be the only alternative. My sump area doesn't have a clear back like some of the newer models so it can't really go in there. The tank is in my bedroom so having a visible light on all night would be a problem. Are there any external refugiums for a nano that anyone's heard of?