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Flow thru Sumps aka Turnover Rate


Let's talk about flow-thru sumps aka the turnover rate of your aquarium. (just my opinion, just like everyone else has theirs)

It used to be an unwritten rule that you had an 8-10x turnover rate in your saltwater aquariums. This was due to many reasons that made perfect sense in their day but is antiquated and just unnecessary with almost all modern equipment. The thought process was since all of your filtrations were in the sump, you had to process all of your water through your sump that many times per hour to efficiently filter and process your aquarium water. This was a factor because most of the early protein skimmers and even mechanical filtration were very poor compared to standards today. Back then most skimmers you went as big as you could fit, just because they worked so poorly you needed that to get the average use from them and they were driven by old wooden airstones. Filter pads were the same way, before socks and modern sumps, you flowed as much heavy flow water thru pads that you could, and changed them almost constantly to keep up.

That was just the way things were. Unfortunately, some of these old school ways of thinking still creep into the modern hobby.

Today, you DO NOT need or want that much flow going through your sump. It's actually bad if you have too much flow. So..........how much flow should you have? That is going to be based on the equipment you have in your sump. The primary basis of what is a good amount of flow is your modern protein skimmer. Gone are the days where you want the biggest you can fit. Now you literally buy the size rated for what or how much you are keeping. So how does this fit into your sump flow aka turnover rate? Your flow through your sump should be 1.5 or 2 x the flow rate of your protein skimmers pump. So if your protein skimmer, for example, utilizes a pump that runs at 150gph, then your general flow through your sump should be around 250-300gph. Here's the reasoning for that. Your skimmer is only going to utilize as much water as the pump inside of it can process. So if your flow thru the sump is too high, then the sump is going to take its little bit, and the rest is just going to go flying past your skimmer, effectively just not even getting filtered at all. Same effect with modern filter pads aka floss or even filter socks. In the old days you used super fast flow and pretty coarse pads. Today, pads are so well made and so fine, that you don't need that massive volume to do the same job.

Now for each additional piece of equipment that utilizes a pump for passing water through it, you can if needed increase your overall flow through your sump by 25%. Usually, it is not needed though. For example media reactors, just don't need excess flow.

So, everyone always starts barking........yea but I need massive flow through my tank for my corals and to keep stuff in suspension and cleanliness.

Well, wake up everyone.............that's what all these modern sometimes high dollar wavemakers and circulation pumps are for.

So, ending with this......"Slow down your flow through your sump, so it can actually do the job it is created for."


What is your estimated flow rate through your sump to your tank? And why?

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