I have a reef ready tank that I'm using as a freshwater planted tank. I have a canister filter setup on the overflow, the intake is inside the box and the output goes up a PVC pipe and through the notch in the side into the tank. All is well in general, but I've run into some issues that I'm unsure how to resolve:

1. I can't fill the tank all the way to the glass brace as I would normally or the water level in the box is even with that of the tank and I don't appear to get the effect of drawing surface junk into the box and down to the filter as I would like. If I lower the water level I can get the level in the box to be lower than the tank and achieve the desired overflow effect.
2. I had the auto-fill sensor outside the box initially, but discovered that the water in the box could drop to zero without kicking on the auto-fill switch. I moved the switch inside the box and it seems to function as desired most of the time.
3. When performing a water change, if the water level drops below the overflow inlet, the filter can pump the box dry in a matter of minutes. This is bad as I put the heater inside the box. It's a metal tube heater which doesn't have an internal thermostat and relies on a temp controller. I had to put the thermometer outside the box because it would kick off too soon as heating the water in the box was much faster than heating it in the entire tank.

The last item is the biggest problem. Short of remembering to turn off the heater and filter prior to lowering the tank water level, it is a real problem. I have considered drilling one or more holes in the lower portion of the box just in case, hoping that it would generally draw from the top most of the time. I have also considered installing a fixed siphon from the bottom of the tank to the bottom of the overflow such that the overflow box will retain the level in the tank at any given time. But again, I would want this functioning only when the tank level dropped as a result of water changes, but I think it would function that way automatically. It just seems like there should be a better way, Am I overlooking something? It does have inlets lower on the box, but they go into a small space that is open to the top and relies on the motion of the overflow water to also siphon water in from these other inlets. So it doesn't help me in this situation. I'm thinking the permanent siphon is the best option unless someone has a better suggestion.

Michael

Ok, well I cant answer all your questions, but just make some observations and maybe suggestions. First, your talking about a tank that has an overflow chamber built into the tank right? And your putting a canister intake into this chamber? I think a lot of your problems are just because your using these overflows not how they were designed (not saying it wont work... but as you've found you have issues). Do you not have any sump at all... just the canister? If that is the case then I dont see a good solution to your problems. Your overflow chambers are basically acting as the sump tank and your canister is the return pump.

1) for the overflow to work properly your water level has to be such that it is at the top of the overflow and only the excess water pumped up by the return pump causes water to flow over the overflow. If you fill your tank all the way up, you basically have a regular tank with a canister filter, just with a somewhat large obstruction around the canisters intake.

2) yeah, the first place your water level is going to decline is in your sump or in your case your overflow chamber acting as a sump. Thats how they work. Either due to evaporation, or doing a wc, your canister will attempt to keep the tank level steady by running your sump until its dry. Your tank level should never drop below the top of the overflow unless your overflow chamber runs dry or you've shut off the pump. Moving the switch and the fill line into the overflow chamber would be the best bet, that way when the levels starts decreasing it will get refilled.

3) same thing as #2 basically

No, there is no sump, but the concept - and really the problems - remain the same.

Imagine that I had a sump and I did a 20% water change. The water level in the tank would drop below the level at which it can flow into the sump. The pump wouldn't know this, so it would continue to pump water back into the tank until the sump ran dry. If the heater was in the sump, it wouldn't know it was dry, and because the thermostat sensor is now exposed to the 70 degree air, it will kick on and overheat.

I purchased a relay today at the electronics supply place and will build a system where if the auto top-off system kicks on because the water level dropped, it will disable the pump and heater until the water level is restored to normal levels.

Michael

The concept is the same, but in order for skimmer to function for extended periods you must use a sump. The internal skimmer of your aquarium does not have the capacity to act as a sump. Either buy one, make your own from an old aquarium or don't use your aquarium with the skimmer function.


Turn off your sump/canister filter/heater during water changes. They are not meant to run during a water change.


The nice thing about a sump is that the water level in the tank stays the same and all evaporation takes place in the sump. Put your heater in the sump and the thermo in the tank. I run sumps at 30% of the aquariums capacity and it will last for 7-10 days due to evaporation. You can always go with a bigger sump. Then put your auto sensor in the sump and it will run nicely.

Good luck, Chris

Michael,

I have one of the 140 RR tank with two overflow boxes. The set up is basically the same setup as yours. I use the glass top to prevent water evaporation and let the water level in the over flow box drop about an inch. Ti heater is in one of the overflow box and sensor in the other. Water change 30% weekly and turn off the heater and both cansiter filters before each WC. The water level in side the overflow never drop... HTH

David