Why am I getting air bubbles in my substrate?

[RTR]

Yup, lifting off the head and turning it on its side or upside down to release the trapped air should do the job.

Mine are all Penguins with the reverse flow kits, which have a rubber stopper at the high point of the flow path, so I just have to remember to remove the stoppers to vent air and replace them before I turn the pumps on again.

Those setups BTW are easy and work well for me. For such an inexpensive pump they are remarkably lasting. I have not used anything else for RFUG since they came on the market. I think they suggest the smaller pump (650?) for RFUG, but I use the 1140 on many (most) setups. If you ever do more, at least look into them. The prefilters are a bit coarse, but with weekly rinsing it has not been a problem for me. My prior DIY setups were a PITA.

 

[Matak]

I was quite fortunate with my DIY setup. I found tubing pieces at my local hardware store that made a good and quick link between my power sponge pump and the inlet tube of the UGF plate. It only takes a couple of minutes to disconect, clean and reconnect the apparatus.

RTR, you said:

I think they suggest the smaller pump (650?) for RFUG, but I use the 1140 on many (most) setups.

Are you quoting litres per hour? If so, I may be grossly under powered. Just checked mine and it is rated at 200 L/Hr. My plate is 12" X 12". Do you recomend that I step up to a higher volume pump? BTW, here is what I use as a pump.

 

[RTR]

No, those are Penguin model numbers of their powerheads which match up to their reverse flow kit. I don't have a 650 still boxed, so can't give a rated output on that model without a web search, but the 1140 is rated at 300 US gallons per hour (or about 1140 liters per hour, so maybe the 650 is nominal liters per hour). I use that on 12x24" plates, 18x18" plates, or 12x30" plates - so from just under 300 square inches to ~360 square inches. Those are all with over-engineered RFUG, giving the plate plus one or two layers of bonded polyester, a layer of fiberglass screen, the eggcrate (no significant flow resistance there) plus 1-4" of gravel - so I am operating high-resistance systems. For plates smaller than those, I use the model 650.

Whether or not you are underpowered depends on how much area you are driving, the fineness of the prefilter, and the depth of your substrate. From the data above, my driving would be at a rated (but actually much lower) flow of about 1 gallon per square inch per hour (or ~3.8 liters per hour). Remember that pump ratings are zero head, and I operate high-resistance systems. If I actually get 20% of rated I would be shocked, but it has been too long since I did that development work - I have vague memories of maybe 15-20% of rated flow with a meter bridged in line (and don't bet the farm on >10 year year old memories), and that would have been with the shallow substrate.

HTH

 

[Matak]

Well RTR, I won't bet the farm, but I'll sure use those ballpark figures as a guideline. I'll figure that being within 50% of your figures is acceptable but if there is a greater than 50% difference, I'll look into a differently powered filter.

I'd like to thank you for taking the time to answer my questions.

 

[RTR]

My pleasure - and associated apologies to Jeremy S whose thread we hijacked - as I hate to see UG/RFUG given a bad rap because folks do not understand how and why they work or what they need to work well.