No problem here, jpsdad. Let me clarify the feed doubling on every 7th day. If I'm feeding 16oz of feed each day, 1-6, on day 7 they get 32oz each. My intent is to see if they are simply still hungry. My goal was instead of assuming the actual weight gain each week, on day 7 by feeding double the normal amount I "should" begin to see that completely disappear at which point I will increase the daily amount going forward the next 6 days. Hope that clears that up, and yes, this is how the hatchery determines feed requirements and was a suggestion that I do the same.
EDIT: The reason for doubling on day 7 is because of logistics raising a massive quantity of fish and the fact it's impractical to weigh the fish to determine % of body weight to feed, so I believe it's more of a short-cut than science.
OK so I am totally good with using a 7 day cycle for increasing feed. The part I was questioning was the doubling part. You won't be able to do it long because the fish won't double in weight each week. The fish will fill up on a proportion of their body weight and this proportion will likely decline a little as they grow bigger. You can imagine that if a fish doubled in weight every week it would be 256 times its original weight in only 8 weeks. So doubling would not be sustainable. I think you would like to feed the fish near satiation if possible and this is the knowledge you will be seeking as a plan of doubling each week. I'd like to offer some ideas for doing that.
First, I would define satiation. Specifically, how much time do they get to complete their meal? Is it 5 minutes, 10 minutes, or something else? Once you know this there is possibly a training period.
So here I recommend starting with a proportion of the fish weight that you feel confident they will consume within the time of the defined satiation time. Time the completion of the meal for each treatment. If the time is less than 75% of the satiation time (whichever takes the most time) then calculate the increase that may make up the difference to 75%. So if the slowest group takes 5 minutes and you allow 10 minutes then increase the following day by 50%. Time again ... etc By the end of the first week, your measurement on the 6th day will be very close to 75% satiation time allowed. If I were comparing two feeds, I would probably not try to accomplish any greater satiation than 80% time allowed in the slowest group of fish. But each week if you time on the 6th day, you would have a good sense of how much you can increase the feed without exceeding the satiation window and without wasting any feed.
The time it takes to complete a feeding is an interesting metric but it may not be without bias. On thought comes to mind. If one treatment always feeds first, then the other treatment may get hyped up waiting for you to stop timing the flurry of activity in the other cage. The treatment that eats last may be ramped up and in a more competitive state waiting its turn. So if that second to get feed is always the same cage of fish, it is possible to introduce bias to their times of consumption. Alternating would remove any possibility of bias in the data as they would each get their respective turns to be first and second. It would be interesting to understand if such would have an effect where possibly they take turns being the fastest to finish. These are just some things to chew on.
