water displacement

Hi everyone, i have a 14 gallon biocube setup now and am preparing to setup my 65gal as a reef tank and have a question. When it comes to adding supplements the instructions say add 1-2ml per 5 gallons, ive made the assumption that they mean per 5 gallons of water. BUT the guy at the lfs said thats based on tank size not actual water volume... is that right? This also makes me wonder about lighting. My biocube has 72watts of light (1actinic 1 10k 1 50/50) Its a 14 gallon tank which give me 5+ watts per gallon, but if i take water displacement from rock and such into account its closer to 9 watts a gallon. first is that too much light and second is my concern over water displacement legitimate. thanks- matt

 

Matt, for the lighting you should take total size of tank, but for supplements you should estimate your total water volume.

Unless you have a TON of live rock and/or a Deep sand bed, the estimation of tank size vs. total water volume should be fairly close. +/- 5 gallons. This has alot to do with how porous live rock is.

 

Not to much lighting. I dose by my tank size.

 

Your assuming right about adding supplements,you need to calculate your actual total water volume including sump or refugium if you have one.I think that the lighting question is a totally different thing.I would worry less about watts per gal. which is an old "rule of thumb" thing and think more about tank depth.There are so many variables when it comes to lighting that it's hard to say what is good or bad using watts per gal.