[Doodaa]

First time poster, year and 1/2 lurker

Some background...
I set up my standard 75 gallon tank 3 years ago as a FOWLR and used 80 lbs. of CaribSea Arogonite which the bag says "seaflor special grade reef sand". I can't tell you the diameter, but it's not close to sand, maybe 2mm diameter or so, it's what I'd call crushed coral. I have about 70 lbs of live rock. But, I also used undergravel filters with powerheads to pull the water through the substrate. I decided to try corals and have cabbage leathers and green star polyps which are doing pretty good. I have added a 30 gallon sump also with CaribSea Aragonite .5-1.0mm dia sand 3" deep and that's where my protien skimmer is along with some Caulerpa andChaetomorpha Algae. I also have a lot of copepods living in both my sump and my display tank.

My problem is algae which probably stems from shutting of the undergravel filter flow and the "crap" trapped in the substrate of my main tank. The algae doesn't bother me much, even though it's not the look I want, because my foxface rabbitfish loves to eat it, but I'm more worried about the nitrates and more sensitive corals I want to add (somewhere down the road). Granted my nitrates are eaten up by the algae and test as 0 ppm, but I want to fix it anyway.

What is recommended? Do I have to tear my tank apart and pull all the substrate and filter plates out? Can I put some finer grain sand on top and leave it like it is? I like the look of a substrate in the display tank, so I don't want to go with a bare bottom. I do have snails and worms and whatever else living in the course substrate I have now. Can I just wait it out until everything gets "recycled" that is in the substrate now? Any opinions or suggestions are quite welcomed! Thanks

[showfish]

IMO, I would ditch the under gravel, not necessary for saltwater applications. If you can, I would replace with a fine grain agronite substrate. I have found that: 1) it does not have as much surface area to collect detrius as larger grains can sometimes do, and 2) It is a better buffer for help with ph. I would also be very careful with both Caulerpa and Chaetomorpha algae in your sump. The two are very likely going to compete with each other and you will have chemical warfare going on in there. IMO, I would ditch the Caulerpa and keep the Chaeto. You don't want that Caulerpa to go asexual on you. Chaeto along with about a 4" to 6" fine grain agronite substrate in your sump will help reduce your nitrates.

[Doodaa]

Thanks Showfish. I didn't think of the competition factor between the two macro's, but for now, I think I have plenty of nitrates due to the other excessive algae I have growing. When it comes down to it, the Chaetomorpha will win for sure.

Does your recomendation for removing all my substrate in the main tank take into account that there is beneficial life in the existing substrate? Will leaving the filter plates in there and the "dead water" it contains below it hurt anything in the long run? Will applying the finer grain sand on top of the existing substrate help/hurt anything?

Obviously, I don't want to tear everything apart to remove the existing substrate and filters, but if that is the majority recommendation, I guess I'll do that.

Thanks again.

[showfish]

Undergravel filters perform similarly to wet/dry filters, but because of their relatively low flow, they are much less efficient. Many marine aquarists have used UGF’s with good success, but they are limited to modest stocking levels and since the entire device acts as a mechanical filter, meticulous maintenance is required to prevent the gravel bed from clogging with detritus. IMO, you may be asking for trouble down the road. You can take the UGF out without having to recycle your tank, for your LR should provide all the nutrification you need. Once removed you can add your new substrate and let things settle. I know this is a big project, but if you want to keep certain types of corals, I think in the long run you will be much better off. Maybe someone else can chime in on this one as well.

[rjs5134]

There's lots of threads on this topic already. I took the advise and removed my Crushed Coral base but haven't replaced it with a fine DSB, YET. I will probably order the sand in the next week or two. Since removal of the CC, I have not had a single outbreak of cyano, algae or any other problem and nitrates have remained at 0+/-.

[Doodaa]

Thanks for the input. I was hoping for someone to come up with a good excuse for me to be lazy. I think I knew I needed to get rid of the stuff. After I've thought about it, I'm not so against a bare bottom tank...should be easier to maintain. And if I get a bit more live rock, I'll cover the viewable bottom. I have some motivation to tear it apart anyway...I want to get my 2 domino damsels out of there.

[wozza]

well this is just me but i would leave it as is, you say you have turned OFF your UGF and it now has dead water under it, this i think is in effect a plenum system not to dissimiler to a DSB.

if you do a search you should find some more stuff on them, some ppl love um some hate um.

What is a plenum?

"A plenum is little more than a vacant space in the substrate, harboring anaerobic bacteria, which converts nitrates into nitrogen. In order for the anaerobic bacteria to function, the plenum must contain carbon dioxide and be devoid of oxygen. If you remove the up tubes and their associated air tubes from an Under Gravel Filter you will essentially have a basic plenum"

cheers james

[Doodaa]

Well, yea, I guess I do have a plenum system. I haven't removed the uplift tubes yet because one is located behind all my live rock and I can't get a good grip on it to twist it out. The other has green polyps growing on it and I haven't decided what to do with them yet.

So, with what I have now, would adding an inch layer of finer sand on top of my about 3" of crushed coral be a good thing? From what I've read, the crushed coral is bad because the detrius falls through it too quickly. I am going to do a thorough cleaning this weekend...either vacuuming the substrate I have and removing the lift tubes, or removing all the substrate. Both instances are going to involve a major water change.

Another reason for wanting substrate in my display tank is for corals that want to be "planted" in it.

[wozza]

hmmm.....i cant help with that one im affraid. hopefull someone else can help!

cheers james

[Doodaa]

All right. I spent 6 hours on Monday cleaning my tank and removing the crushed coral and UG filters. I knew that was going to be a chore, but I didn't think it would take that long. So, now I have a few new questions...

1) Do I need to vacuum the sand in my refugium or let the detrius collect there and wait for bacteria, algae, and amphipods eat it? I am not sure if I have copepods like I stated earlier, but I know I have amphipods. I also got rid of the Caulerpa and only have Chaetomorpha Algae.

2) How do I clean my new bare bottom tank with all the live rock and someday lots of corals in the way? Variable current and the overflow to the sump/refugium or should I use some small tubing and siphon it out or both?

Thanks again for helping a newbie with this awesome forum