Two Overflows - Two Returns - Two water levels, will it work?

kput · Aug 13, 2020

Hello all, I am in the process of turning a stock tank into a mimicked tide pool. One of the challenges I'm facing is how to mimic high and low tide in the tank.
I have a build thread where I detail my idea, but haven't gotten many responses, figured I'd make a post here looking for some DIY Advice.

Build Thread 100 Gallon Stock Tank - Mimicked Tide Pool

I'm acquiring two 100 gallon oval shaped stock tanks to use in moving my display. I've decided to turn them into my own little tide pool. It will be stocked with numerous inverts, mollusks, anenomes, starfish, urchins, and other animals often found in tide pools, I will try my best to closely...

www.reef2reef.com

The stock tank has one 2" overflow and bulkhead drilled already. My idea, is to add a second overflow roughly 8" below the first. Ball valves directly off of each overflow, into a tee, into a 2.5" line, and into the sump. I'd have a piece at the top going above the water line with a hole drilled for the overflow, and figured two 2" lines should probably go into a larger 2.5" pipe to accommodate all the flow? Is this accurate?

I would then set up the return pumps on a timer. One running all the time, the second on schedule. When both pumps are on, I would have the water flow all the way to the second overflow. Timer shuts off the pump, and the water level would then drop to the second overflow, simulating low flow.

Does this idea seem sound? I'd have the ball valves on each drain so I can tinker with the out-flow if needed. Planning on getting my hands on some mag-drives to run everything. (Please don't tell me to just get an Apex and ramp pumps up and down, I'm going for a budget build lol).

This photo is a rough (I'm a talented artist...) sketch of what I'm planning.

WVNed · Aug 13, 2020

I think I would consider making it like a surge device.
One pump fills a tank till it rushes back.

I always wanted to try making something using a self starting bell siphon. Never got around to it.

sharpimage · Aug 13, 2020

If the lower drain was really small and at low tide there was little flow, I could see this working. Might smell though

chipmunkofdoom2 · Aug 13, 2020

This would probably work if you didn't make the main drain too low in the tank. It seems overly complex though. The water level is not necessarily the important part, it's the difference between the low and high flow.

Why not just oversize a single drain? Have your main drain big enough to accomodate something like 30 GPM. Have your main return pump deliver a constant flow at something like 15 GPM. Have your secondary return pump deliver something like 10 GPM. This gives you variable flow (higher flow when pump 2 is on) and has the additional benefit of giving you a constant sump and tank level.

kput · Aug 13, 2020

WVNed said:
I think I would consider making it like a surge device.
One pump fills a tank till it rushes back.

I always wanted to try making something using a self starting bell siphon. Never got around to it.

I will have a surge tank running seperate from the two-overflow system, likely going with the carson bucket method due to simplicity and lack of wearable parts.

chipmunkofdoom2 said:
This would probably work if you didn't make the main drain too low in the tank. It seems overly complex though. The water level is not necessarily the important part, it's the difference between the low and high flow.

Why not just oversize a single drain? Have your main drain big enough to accomodate something like 30 GPM. Have your main return pump deliver a constant flow at something like 15 GPM. Have your secondary return pump deliver something like 10 GPM. This gives you variable flow (higher flow when pump 2 is on) and has the additional benefit of giving you a constant sump and tank level.

I'm trying to make this as close to accurate on a real tide pool as possible, so the different water heights are important. Just like in nature, tide pools partially drain throughout the day, leaving rockwork and critters exposed, this is what I want to mimic.
I will have one or two gyres, and a surge tank to provide my high and low flow.

I'm also planning on combatting the inconsistent sump levels by using an external skimmer with a pump feeding it, and water being pumped in automatically throughout the day, rather than using a true ATO system.

bct15 · Aug 13, 2020

Out of curiosity, why are you creating the tide pool?

When your lower drain becomes fully submerged, it will become a siphon drain and pull a lot of water.

WVNed · Aug 13, 2020

Pump the water uphill. Control how long it takes to drain back with a valve.

kput · Aug 13, 2020

bct15 said:
Out of curiosity, why are you creating the tide pool?

When your lower drain becomes fully submerged, it will become a siphon drain and pull a lot of water.

The lower drain/overflow will always be fully submerged, with the top overflow being submerged frequently as well (planning on 3-4 90 minute low-tide scenarios throughout the day). Are you saying the lower drain will behave differently than a typical overflow due to having the second overflow above it?

(I guess overflows aren't the appropriate term here.. I mean drains lol, just running elbows like you would in an overflow setup)

I acquired these stock tanks for a tank move. I had room in my basement for something, a spare chiller, free time and a couple tanks to play with so this seemed like a pretty neat idea. I haven't seen a true tide pool tank in all my research so I'm thinking this will be a first.

I wanted to do something unique, and fun, but also something that can be viewed from the top since I'm not working with a glass tank. My wife also loves the ocean, and this will be pretty similar to a "touch tank" found in large public aquariums, so she can touch some of the starfish and urchins without going elbow deep in my display lol.