You can always add a PVC ball valve and some Barb fittings to attach it and use it to turn down flow.

 

Myself I would go big if you are just going to run one filter. As soon as it arrives I'll be running two 206's on my 45g. Myself I would favour two smaller filters then one big one. I think it adds versatility and redundancy. Two outputs is nice for getting the flow in the tank just right(I currently run a 206 and a ac30 HOB) Maybe two 207's could work for you? Or maybe you could supplement the smaller filter you already have with another smaller one? I think one thing for certain is that at some point in time a filter is going to have an issue, impeller, leak, whatever. Having two will seem very convenient if you need to wait on parts or don't have the time to deal with it immediately.

 

I'm running a 307 on a 29 with and inline heater. I run it wide open and its perfect. You can adjust flow with the Aquastop lever. Get the 407 for a 55. You will not regret it.

The 407 output is only 245 gph. By the time you customize media it will reduce flow even more.

I also agree with Squisher on the two filters. On that same 29 there is a Sicce Whale 200 running next to the 307.

 

That's another plus of the two canister filter setup is if you run inline accessories you have more lines to work with. I'm currently running an inline co2 diffuser on my one 206 and on the new one I'm going to run a inline air diffuser and eventually a inline heater. I had considered a 207 as my second filter but liked the idea more of having two of the same then I can have one little stash of spare parts that fits both filters.

The only downside I can see is some increased maintenance. Two filters and sets of lines to clean.

 

Good point. I'm actually running a 203 right now and have a 2nd one I inherited from someone. Yep...these things seem to run forever. I hope the new ones are just as reliable. I would end up with more cleaning and a lot of tubes running around with two. It is in my living room. I think the new ones have a flow control and with the media further reducing it I'm leaning toward the 407.

Wow. That sounds like a lot of filtration with two filters on a 29. What is your plant and fish stock? I actually have my old undergravel filter on the 55 tank still. It is a leftover from before I got more into plants and I didn't want to break everything down to get it out. I've left it as a backup to supplement the 203 but that combo does not work as well as the newer higher volume filters hence the upgrade. At some point I will pull out the old undergravel filter.

 

Good point. I'm actually running a 203 right now and have a 2nd one I inherited from someone. Yep...these things seem to run forever. I hope the new ones are just as reliable. I would end up with more cleaning and a lot of tubes running around with two. It is in my living room. I think the new ones have a flow control and with the media further reducing it I'm leaning toward the 407.

Wow. That sounds like a lot of filtration with two filters on a 29. What is your plant and fish stock? I actually have my old undergravel filter on the 55 tank still. It is a leftover from before I got more into plants and I didn't want to break everything down to get it out. I've left it as a backup to supplement the 203 but that combo does not work as well as the newer higher volume filters hence the upgrade. At some point I will pull out the old undergravel filter.

I have always over filtered my tanks. The fish load 29 is extremely heavy and it is very densely planted. I would not get the even flow I want with either one of the canisters. I also don't like additional power-heads in such a small tank. So I run two canisters. I have have traditionally ran two on all my tanks except very small ones. I run a 107 on a 45p and a 2011 on a 5 gallon. Its always easier to reduce flow than increase.

 

I had a 307 on my 40B and I had to throttle it down to not blow everything around. Had a spray bar across back of tank. Could have gone with a 207 and been fine more then likely.

My opinion but I did not like the throttling on the 307 style filters. Nor do I like that whole portion of the filter (where the hoses connect to the housing). Its improved on vs older styles but it still leaves alot to be desired IMHO. The internals were arranged pretty good and alot of room for stuff. I changed to black tygon tubing and made my own spray bar for it which worked well.

I like my oase 350 better however it is not perfect either. It does have a little better tamper resistance for younger ones (more difficult to open or remove hose connection and canister top). The way I run mine with a prefilter and the removable internal prefilter sponge its easy to clean those portions. I rarely clean the rest of the inside although its probably getting close to time for that. Another aspect is the flow control is via a valve built into the hose connection on lip of the tank top (where you attach the spray bar or nozzle essentially) which makes it easy to adjust flow.

The 307 has more flow then the 350 but in my situation that is ok oh and no ribbed tubing.

 

I went from 306 to 407 on my 55 and happy I did so. You also don’t need to install a valve.

Here’s from their manual

“ Once the filter is operating continuously, you can use the top lever on the AquaStop to regulate the water flow.
To reduce the water flow, lift the lever up to halfway, but no higher. This can be done once the unit is fully operational, and will not harm the motor. However, never run the filter with the lever up (closed) more than half way.”

 

A lily pipe on the outflow will greatly reduce turbulence without hurting flow.

 

I'm planning to swap the ribbed tubing for the Eheim 16/22 green vinyl tubing which I read is a good fit. It needs to work with diffuser too. I see a few different spray bars offered. The Fluval one looks a bit short for a 4' long tank. Flow tamer makes a longer black one. If they are still 1/2" diameter I might try to reuse my old one but I would need an elbow.

 

I plumbed my inline diffuser into the ribbed tubing by just using fluvals rubber hose adapters.

 

What was your diffuser size? Could you connect it directly to the adapters or did you need a short section of tubing between the adaptor and the diffuser?

 

My inline diffuser is the co2 art 16/22 size. So it was a direct fit/splice in with these fluval rubber hose adapters, no line or further adaption nescessary. One end fits on the ribbed hose, the other on the diffuser. https://www.amazon.ca/gp/product/B0006JLOCI/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1

 

I ended up getting the Oase Biomaster inlet/outlet kits to hook up to my Fluval 307. The Oase kits have flow control built into the inlet/outlet.

 

Just going to reiterate what others here have said, Just do the 407, you will want that extra flow option. Plus if it holds more media, that's cool, I don't think there is a difference in those two. But I don't know.

Anyway, you can reduce the flow on Fluval canisters and the media will drop the flow from the listed GPH. The listed GPH is usually when it's tested with no media in it at all. no sponges, I wouldn't be surprised if they took out the media baskets and the sponge holders too.