Undergravel with plants?

[mugwuch]

Just thought I'd ask if plants do ok with undergravel filters. I have been told so many times that they don't do well, something to do with oxygen being drawn over the roots. Any ideas? I only ask because mine don't seem to be doing so good.

 

[Lateral Line]

It is certainly true that plants do not do as well with ugf's as they otherwise would, however, there are many people, including me in the past, who have had reasonable plant growth with ugf's. In the wild, plants do not have oxygen rich water circulating around their roots, they tend to be rooted in fine silts and mud with hardly any water movement at all.

What kind of plants do you have, what size is your tank, and how much light do you have over them?

 

[mugwuch]

Well, I have a 20 Gallon tank, with 1x 25w 18k bulb, and 1x 20w tropical bulb. have the following plants in approx 3" of substrate. Anubias Balteri var. Nana, four off. Echinodorus Macrophyllus, four off. Echinodorus Uruquayensis, two off. Then finally, Gymnocoronis Spilantoides, two off. All spellings are approximate. I am thinking of buying a CO2 kit, do you think this would help? I must add that I do add plant food, and keep the lights on for 10-12 hours a day, and have very little or no algae growth since planting the tank out, which I am very happy about! Some have black edges, others appear to have rotted out in the leaves. I cut them back when I spot this, and some have brown spots. I really want this to work as the fish seem to really love this environment, and I want to sort it out. What are your recommendations?

 

[babyfish]

You can try planting your plants in pots, this way you can make sure they have a nutrient rich substrate which you then cover with gravel in the tank.

 

[faewyn]

I have an undergravel filter and over the past 11 years I have not had any problems with plants not growing, apart from fish nibbling them!
I dont use and fertilisers etc. I was told years ago that you need at least 6cm of gravel for them to thrive, I have 4cm.
All i do for my tank is, check the pH once a week, and change 25% every 14 days and everything is left up to nature
I have only gone tropical in the last 3 months, I my plants (tropical) are thriving.
I wish you all the luck!

 

[Lateral Line]

You have a good substrate depth there, I am inclined against pointing the finger solely at your ugf installation.

All the plants you list are medium to bright light demanding species, but are pretty easy plants, which whilst they may benefit from CO2, do not demand it. Medium is usually quoted as 2 Watts per gallon in a regular rectangular tank, (if it's a hex you'd need more). You have sufficient wattage. What I am a little suspicious of however, is your choice of lamp. In particular, the 18,000K lamp. The spectrum that lamp produces does not cover a great deal of the spectrum absorbed by chlorophyll. If I were you, before trying anything else, I would take that tube out and put a 6,000K tube in it's place.

 

[mugwuch]

Thanks very much guys, for your help. I have bought a 6000K tube, and a new tropical spectrum tube, and added some reflectors as well. I spent a lot of time investigating on the net at the weekend, hence the late reply to say thanks. Seems my tropical tube was a little old at a year, and could do with replacing, so in went the two new ones and some reflectors. How much will I benefit from the reflectors? I'm a little worried they will make the tubes age prematurely, because of the heat being held in. The guy at the the LFS said that they would give me an extra 30% light output. The plants are working, my nitrate levels have fallen from 50mg per litre to 10mg per litre in two weeks! They seem to be on the way down big time. The only down side is I can't catch all the fry that arrived at the weekend! Thanks again. I'll keep you informed on any improvements.

 

[Lateral Line]

The phosphors used in todays multiphosphor fluorescent lamps do not age anything like as much as the older types, and the "aging" is not heat related. The single biggest contributary cause to todays lamps fading in electrical ineffeciencies in the elctrodes at either end of the tube, which is a function of quality, thus cost. A good quality modern multi-phosphor tube has a relatively constant light output for a long period and then fails quite rapidly. The reflectors should not affect the longevity of the lamp.

I don't use any "fancy spectrum" lamps, only full spectrum tubes of between 5,500K and 6,500K so I have a CRI of well over 90 - the colours look right. Some people like the colour effects they get with a mixture of lamp types though. Whatever, for plants, you need to be providing the frequencies that chlorophyll absorbs.

You sound like you know what you are doing - good luck.