My fry tank has been slowly going green over the last 2 weeks. I have let it so far because I have heard that green water is good for fry as they can get nurtition throught the day as they want. However, I am leaving for vacation in a week and my grandma will be feeding and monitoring the tanks while I am gone. The fry will be about 3 1/2 months old. There is a light amount of green algae on the glass, but its the free floating stuff that I'm undecided on keeping or removing.

I have been going back and forth over should I leave the tank green, or work on getting rid of the algae. I see benefits to both sides, and not so benefits.

Pros on keeping it green:
Fry have ready snacks while I am gone, since that will be getting fewer meals.
the algae eats up some of the nitrates and would keep them lower for the 13 days that there will be no waterhanges.

Pros on clearing it:
Easier for my grandma to do a fish and equipment check. (right now its hard to see the bubbles)
IF there was an equipment malfunction, less chance of suffocation of the fish overnight.
Easier for all the fry to see the food at feeding time.

Cons on clearing the algae:
it is possible I have let the algae take over (starve out) part of the cycle, and by removing it I would be back to an uncycled tank with no waterchanges for almost 2 weeks.

What would you do in my situation? If I am going to try to remove it I need to start the upped waterchanges by monday to have a good chance at removing most of before the trip.

Well, green algae is definitely a great food for all fish, especially fry. I would say, clear the front glass so she can see what's going on inside the tank and leave the rest. Actually, all plant growth, algae included, create oxygen, not take it away. Also, if your grandma is the stereotypical "love 'em and spoil 'em" grandma, I'd also say to hide the fish food. Pre-measure out each day's food and put in it one of those 7 day pill boxes and tell her to just feed your fish what's in each corresponding box for each day you're gone. That way she won't overfeed out of love.

The algae is not just growing on the glass...the water itself is green with it. The stuff on the glass is not the problem atm.

My grandma has fed my fish before. We use the pillbox method for the adult fish. The fry get crushed food, fed with a toothpick. She does not overfeed There is a tank in the kitchen, and one in the living room, with the food in/on the stands all the time. She never feeds them even though they are all expert beggars. (We have this agreement: She feeds my fish when I am gone, and I water her plants when she is gone.)

ah hah... well, you have grandma trained, so at least that's not a worry. Have you asked grandma to look at the tank with the green water to see if she feels comfortable with it? It would be nice to keep the green water I would think, but if it could affect how she's able to take care of them, I would think it might not be worth it. I wonder if you could take out the green water for her while you're gone, but save it and then put it back when you return? Just a thought.... Let's see if someone more knowledgeable has any opinions...

As long as your grandmother is comfortable with caring for the fry in a green water environment, I think I would vote to leave it. How would you "clear" it anyway? The BEST way is with a UV.....really the only way in my opinion other than a 100% water change and scrub.

Since you have to do a really large water change before you leave to get the tank ready for that awful 13 days between changes, you will be diluting the green down to very low levels. It should be very lightly green at that time. Over the next 13 days, it will thicken, but at least you will have 5-6 days without it being so thick Grandma has difficulties.....

I think the fact that the green algae will process the nitrates in a tank that is fully fed and left for 13 days far outweighes the potential for power outaages. The fish will have no difficulties finding the food - fish find food even if they are blind. And as far as starving out your cycle - no chance of that, either. Green water systems are not quite as efficiant - at least in speed - as the beneficial bacteria that make up the nitrogen cycle. They will not be able to outshoot the bacteria for the ammonia. The algae will feed mostly on the nitrate. In a true greenwater system, they only have the ammonia, but the nitrate is much easier to process.

Show your grandmother ways to check for the bubbles if you wish. Change out a very large amount of water before leaving (90% would be my choice). Have Grandma feed VERY sparingly - with fry it is difficult, but can be done with care. The go with a clear mind.

I do have a uv sterilizer I can put in that tank. Its not good enough to kill parasites and bacteria that I know of, but give it 2 days and all free floating algae is gone in any tank.

The food. If I leave it green then I think I will have her give them 2 dry meals a day. Their dry meals are two dips of the toothpick into the tank then the crushed food, then the tank again. Oh and some of the adult food gets dropped in whole for them to nibble on after they gulp down the crushed chunks.

I have to talk to her tomorrow about the tank feedings and light schedules. I will bring her upstairs and see what she thinks about the green tank (besides "Its ugly and I'm glad its not in my kitchen anymore!"). She hates the look of any green tank, but so far has not nagged me about it since its in my room.

And I worry about the bubbles because I have it running off a split line from one pump, with an airflow adjuster on it. About once a week or so I have had to fiddle with the airflow valve because I wake up and no more bubbles. Some of the fry are still too small for me to let it run full flow.